.NET ShortCut

Blog Moved

2007-05-06T22:59:00.000+03:00

i moved to http://blogs.msdn.com/HusseinA

2006-11-25T14:12:00.000+03:00

Why BTS 2006 Host Process can be Clustered ?

High Availability in BTS is provided using host instances in the same Biztalk Server group . so why do we need to Cluster BTS Host Process ?

1- Concurrency

Problem Statement : If an adapter handlers running inside an unclustered host process , this means that this adapter is running simultaneously on all the host instances. so let's say that all instances are accessing a shared resource , so we have a concurrency violation access issue here .

a typical example is FTP Adapter that is using FTP Protocol : so if all instances are accessing the same FTP location using FTP protocol , this will lead to concurrency problems since FTP protocol doesnt put any locks on the accessed files.

solution : make the FTP adapter clustered so we got high availability and in the same time , removing concurrency issues.

2- Ordered Delivery

Problem Statement : in case of MSMQ adapter for example : it delivers the messages in the order that messages have been received . so if we have two MSMQ running in two host instances we might lose this order delivery behaviour.

Solution : make only one adapter running at a time and getting high availability for that adapter by clustering the adapter.

for how to Implement the Clustering Itslef : http://www.microsoft.com/technet/prodtechnol/biztalk/2006/library/bts06clustering/cd301e18-ca9a-4b33-b57d-f03bff750521.mspx

2006-11-15T17:08:00.000+03:00

How To change the Database Server Location and DB Names for BizTalk Server

Foe BizTalk Server 2004: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/operations/htm/ebiz_ops_backuprestore_prqu.asp

For BizTalk Server 2006: http://msdn2.microsoft.com/en-us/library/aa559835.aspx

2006-11-08T11:05:00.000+03:00

Never ever change snk files during development

assembly 1 is signed with snk 1 . alot of apps are using assembly 1. a developer for some reasons created a new snk file and resigned the assembly and redeployed it. i know that all of us know that all apps will not work. but this really happens alot with developers. i faced it alot with my developers in the last month so i decided to write about it.

snk is not a configuration that we can change . think about it like a critical change where all the behaviours of the application will change.

2006-10-10T16:38:00.000+03:00

WSS Web Parts vs ASP.NET 2.0 Web Parts

a good comparison between WSS web parts and ASP.NET 2.0 web parts is here by Ted Pattison : http://pluralsight.com/blogs/ted/archive/2005/06/01/9697.aspx

2006-10-10T16:22:00.000+03:00

msdn wiki has been released

http://msdnwiki.microsoft.com

2006-09-22T20:21:00.000+03:00

BizTalk Rules Parameters not Appearing in CallRules Shape in Orchestration :

i spend some quite time figuring out what was the problem , so i would like to share this with everyone.

after i created a rule in Biztalk rule composer , i created an orchestration with a callrules shape that points to the rule i created , but no properties appear in the window. i want to add a message as an input .

Solution : the "fully qualified name" for schema must = document type for a fact

1- go to the schema1.xsd file that you have created initially and built your facts on

2- highlight the .xsd file in solution explorer

3- copy the "fully qualified name" property value from the properties window

4- goto your vocabularies

5- create a fact based on XML schema

6- in the fact definition window , in the document type property : paste the "fully qualified name"

if you have already published your vocabulary , copy and create a new version , and then create new rules based on the new vocabulary . you will notice the vocabulary version in the properties window

I love this Feature, I really love it

2006-05-01T22:34:00.000+03:00

Aspnet_regiis -ga MachineName\user1

This command gives user1 privileges to access the IIS metabase . In short it
gives this account permissions so it can now be an identity of an
application pool in IIS .
In v1.1 we don't have this switch (-ga) . So I used to grant all the rights
and permissions manually ...

I love the ga switch :)

Referencing 2 versions of the same DLL at the same time

2006-04-25T17:56:00.000+03:00

I need this feature in VB
,Pleeeeeeeaaaaaaaaassssssseeeeeeeeeeeeeeeeeeeeeeeeeeee
Only C# has this feature nowwwwwwwww :(

You can do this in C# :
Csc /r:ver1=assembly1.dll /r:ver2=c:\assembly1.dll myapp.cs

Here is a sample of myapp.cs file
extern alias ver1;
extern alias ver2;

using System;

class MyApp
{
static void Main(string[] args)
{
Console.WriteLine(ver1::MyLibrary.Class1.Test());

Console.WriteLine(ver2::MyLibrary.Class1.Test());
}
}

Connection Pooling

2006-04-23T15:18:00.000+03:00

This is a very interesting funny notice :
Connection Strings must be IDENTICAL . so what is new ?

Conn1 : "Server=SQL01;Database=AdventureWorks;Integrated
Security=SSPI;Pooling=true"
Conn2 : "Server=SQL01;Database=AdventureWorks;Integrated Security=SSPI
;Pooling=true"

These are not identical since the second connection string has a SPACE after
the word SSPI, so they generate two different pools.you can examine that by
SQL Profiler .
It is very interesting ha .

Connection Pooling Series or parallel ?

2006-04-22T14:58:00.000+03:00

If we have a connection like this :

Conn1 : "Server=SQL01;Database=AdventureWorks;Integrated
Security=SSPI;Pooling=true;Min Pool Size=100"

Are the 100 connections created in series(one after the other) or
parallel(all nearly at the same time) ?
To avoid Flooding the Database with Connections they are created in series .
You can check that by executing the above connection and notice the
"starttime" column in Profiler , you will notice in the profiler that they
are opened serially after each other by fractions of seconds.

Why do I have to press CTRL+ALT+DELETE to logon

2006-04-19T03:52:00.000+03:00

Why don't the logon screen just appears directly without having to press
this combination ?
As Keith Brown says in his book "A .NET Developer's Guide to Windows
Security" . Always Asking the user for his password trains the user to
always type his password whenever asked. And since it can be any
malicious code asking the user for his password so logon screens must be
kept to minimal.
The Sequence of CTRL+ALT+DELETE can only be traced by Kernel mode , so
this is a clear message from the user to the OS that "I need to type my
password to logon". This Sequence cannot be tracked by user mode. So try
seriously to use the logon user account instead of asking him.

VB VB VB

2006-04-18T15:54:00.000+03:00

Unfortunately I still see some developers and architects see that VB is
untrustable and you still cant do a lot of things using VB, I would say to
those people "please read the Developer Division Manager Somasegar's blog
entry" http://blogs.msdn.com/somasegar/archive/2004/08/01/204540.aspx

And you can read also the Man behind VB's Blog entry :
http://www.panopticoncentral.net/archive/2004/05/31/1100.aspx

I hope you completely change your mind now specially when you know that a
lot of .NET 2.0 classes have been written entirely with VB as well as the VB
engine itself and parts of the VS IDE.

The comparison between C# and VB.NET now becomes like "which of my 2 eyes I
like better " as SomaSegar has said .i really like this phrase

Impersonation in .NET

2006-04-18T01:54:00.000+03:00

Impersonation is done on a thread basis not on a process level. So when we say that something is impersonating a user, then this something must be for sure a Thread not a process.
A thread impersonating a specific user means that the thread will be working with the security context of that user.
New created processes inherits their parents’ tokens
When a thread needs to stop impersonation for a while for example in ASP.NET if we used impersonation in web.config and a certain page needs to do a task with a specific privilege regardless the impersonated account then in that case we have to stop impersonation temporarily . there is a specific function to call in this case called “RevertToSelf”
We can do this in .NET by :

Console.WriteLine(WindowsIdentity.GetCurrent().Name); //print the impersonated account name

//RevertToSelf
//This line will remove the token impersonated and will revert back to the process identity.
WindowsImpersonationContext c = WindowsIdentity.Impersonate(System.IntPtr.Zero);

Console.WriteLine(WindowsIdentity.GetCurrent().Name); //print the process identity account name

//go back to Imopersonation
c.Undo(); // will get the impersonated token back
Console.WriteLine(WindowsIdentity.GetCurrent().Name); //print the impersonated account name
Flow of tokens to new threads is different in .NET 1.1 than 2.0
in the image above you can see...

Step1
A process running under Administrator Token. And a thread that is running under the same account

Step2
The thread impersonates HusseinA.

Step3
The current thread in the process spawns a new thread

If thread1 spawned a new thread, what will be the token flown from thread1 to the spawned thread.

In .NET v1.1 it is the original Process token which is Administrator in this case.
Example: if a process running under “local system” and a thread in this process impersonated another lower privilege account then the current thread decided to spawn another thread. the new thread will run under local system not under the impersonated account. This is very dangerous and can lead to some flaws.

In .NET 2.0 the default now is to flow the impersonated account and not the original process account.

using System;
using System.Text;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Principal;
using System.Threading;

namespace ImpersonateTest
{
class Program
{

[DllImport("advapi32.dll", SetLastError = true)]
static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword,
int dwLogonType, int dwLogonProvider, ref IntPtr phToken);

static void Main(string[] args)
{
//get a token for a user
IntPtr token = IntPtr.Zero;;
bool loggedin = LogonUser("user1", "MyMachine", "P@ssw0rd", 3, 0, ref token);
//prints the name of the process identity name Console.WriteLine(WindowsIdentity.GetCurrent().Name);

//Impersonate
WindowsIdentity w = new WindowsIdentity(token);
WindowsImpersonationContext oldWindowsIdentity = w.Impersonate();

//prints the name of the Impersonated account name Console.WriteLine(WindowsIdentity.GetCurrent().Name);

Thread t1 = new Thread(new ThreadStart(Test));
t1.Start();
}
static void Test()
{
//in .NET 1.1 prints the name of the Process account name
//in .NET 2.0 prints the name of the Impersonated account name
Console.WriteLine(WindowsIdentity.GetCurrent().name);
}
}
}

Web Application Projects vs Web Site Projects

2006-04-09T10:48:00.000+03:00

The motivation for building a new Application Project Model :
http://weblogs.asp.net/scottgu/archive/2005/12/07/432630.aspx

A very useful comparison between the two models :
http://msdn.microsoft.com/vstudio/default.aspx?pull=/library/en-us/dnvs05/html/WAP.asp

Very useful Tutorials :
http://webproject.scottgu.com/CSharp/Default.aspx

Data Driven Unit Test

2006-03-27T18:11:00.000+03:00

TDD :

You will hear a lot about it in the VSTS era

Test driven development :

It is not testing software ,NO
It is aligning the developers to write more code efficient from customer
point of view

So life cycle would be :
- Write test (what ? Without having a code to test it) yes , write test
projects first . Think from customer point of view: what I need this
software to behave like . For example : I need my method to return
InvalidCustomerIDException when someone passes a null of invalid ID, and
I begin writing the test for the method that doesn't exist yet. So I
force the production in this way to follow the behaviour that I have
already designed in the test

- run test and see it fails . In this way I know that there is something
that must be done in the production code to make the test succeed

- write production code that make the test pass

- run test and see it pass

Ok here comes the main goal for this feed entry :
When I write a unit test , I am writing a static expected value and
calculate the actual value and then compare by Assert .what if I need
these values to be dynamic or having many values ? I will write an array
of course in the test method and loop through the array and invoke the
production code, WRONG.
There is another smart way: Data Driven unit test
I will create a table in the DB , and fill the table with data and tell
the test engine : please invoke my test method number of times equals
the no of rows in the table and pass the value for each row to the test
method every time. Wowwwwwwwwwwwwwwwwwwwwwwwwwwwww magnificent
So any time I can go to the table and change the test data and have
another punch of tested values.

Visual Studio 2005 Web Application Projects

2006-03-27T18:10:00.000+03:00

Now we have two environments for building ASP.NET II web sites

1- Visual Studio 2005 Web Application Projects Model (Similar to VS
2003)
2- Visual Studio 2005 Web Site Projects Model (the new 2005
model)

You can download the web app model from here :
http://msdn.microsoft.com/asp.net/reference/infrastructure/wap/default.a
spx

This VS 2003 model style will be merged with VS 2005 SP1

And please no one ask me why we have two models ?
From my point of view : it is left for your flavour .
And one more thing :

Migration from VS 2003 web projects to VS 2005 web projects will be
straight forward as they are the same model .

Deploy Web Part in GAC or in /bin

2006-03-05T18:37:00.000+03:00

There is only 1 difference : Security

Web parts deployed in GAC run always under full trust without any CAS
restrictions
Web parts deployed in /bin follow any of the five CAS trust levels
defined in web.config .

BTW : "Trust Levels" is a feature provided by ASP.NET II

Is Runnable DLL taking over EXE ?

2006-03-05T17:28:00.000+03:00

Till the launch of .NET 1.1 there were some difference between DLLs and EXEs
:

1- you cannot reference /r an EXE in your project but you can reference a
DLL
2- you cannot deploy an EXE in GAC (Gacutil) but you can do so with DLL
3- DLL never meant to be runnable (has an entry point) but EXE does

After launching .NET 2.0 everything have changed now :
1- you can reference an EXE as well as DLL
2- you can Deploy EXEs in GAC
3- you can have a runnable DLL, yes you heard me , you can have a complete
project(like a windows forms APP) inside a DLL and run it .although this is
not documented, but it can be easily done .

So the question now is :
are DLLs taking over EXEs ? It can if it wants to
Are EXEs taking over DLLs ? It can if it wants to

There is still only one difference between them , which is the concept of
"Stand alone runnable APP". If I have a windows or a web or a mobile control
as EXE , I wouldn't know if I need to double click on it to make it run or
just add a reference to it in my app. So the logical meaning beyond the
extension is still there .

I Already Have MARS in SQL 2000

2006-02-22T14:52:00.000+03:00

Can we really have Mars in SQL 2000 ? The answer is yes to some limit

pIDBCreateCommand->CreateCommand(NULL, IID_ICommandText, (IUnknown**)
&pICommandText);
pIDBCreateCommand->CreateCommand(NULL, IID_ICommandText, (IUnknown**)
&pICommandText2);
pICommandText->SetCommandText(DBGUID_DBSQL,
OLESTR("select operation_id, operation_code, product_id, quantity
from dbo.operations where processed=0"));
pICommandText2->SetCommandText(DBGUID_DBSQL,OLESTR("update dbo.operations
set processed=1 where operation_id=?"));
//Execute the command
pICommandText->Execute(NULL, IID_IRowset, NULL, &cRowsAffected, (IUnknown**)
&pIRowset);
..
ProcessOperation();
..
//Execute the command 2
pICommandText2->Execute(NULL, IID_IRowset, NULL, &cRowsAffected, NULL);

What does SQLOLEDB does in the background ? It opens a new connection . What
? Yes you heard me . It opens a new connection and execute command2

Some Scenarios :
1- what happens if command1 was in a DTC TX ?
in this case SQLOLEDB cannot open a new connection and command2
fails
2-Command1 in a TSQL TX not a DTC TX ?
SQLOLEDB has no idea that command1 is in a TX and it will open a new
one, ending in two command living in different TX.
3- think about more scenarios like locking (2 commands lock each other )
There are a lot of more scenarios to be covered but no time

Any way , again the answer of the question is YES of course we do support
MARS in SQL 2000 behind the scene

The binding handle is invalid

2006-02-21T13:36:00.000+03:00

At last I found a solution for this problem .
Problem : when you start debuggin on Visual Studio 2005 you get this
message . Some people disable generating the vshost files which are
important
But the solution is : go to the terminal services windows service and
change the startup option to be manual and restart the computer or make
it manual and start it without starting the computer

Change configuration profile in 2005

2006-02-19T17:54:00.000+03:00

If you want to change the configuration Profile from Debug to Release in
2005 , some people go to application properties designer and from (Compile
or Build) they change the configuration to Debug or Release . This is wrong
This allows you only to change the settings of each profile , but if you
want to change the current running active profile you have to go to menu
Build\Configuration Manager and change it

vshost

2006-02-18T15:42:00.000+03:00

What are vshost files : "app.vshost.exe" and "app.vshost.exe.config" ?

Vshost files are used at design time only and they are used for 3 purposes :

* improved F5 performance. Keep the state of appdomains between runs
of my application. So before running the app for 2nd time , the vshost
preserve the state of appdomain so saving sometime to reinitialize
everything

* partial trust debugging

* design time expression evaluation. Which has taken out from VB2003
and now is back for all langs .you can use the immediate windows in design
mode for some design time expressions evaluation we need,

Why Do we need AppDomains ?

2005-12-20T14:44:00.000+03:00

1- a place to load unload assemblies
2- isolation
3- security (assemblies inside same appdomain can have same policy)
4- configuration

A very powerful feature that has been taken for 6 years , now is back

2005-12-12T02:53:00.000+03:00

VB DTEE ...............
Yes it is back , I cannot believe that . I deadly needed this feature in
2002 and 2003. and I always wanted to see the one in charge who has removed
this feature , but fortunately now I wont be searching for him any more :)

Now (in 2005) I can open the immediate window without running the program at
all and execute commands .without running my program I can invoke a function
, evaluate an expression , create an object , anything !!!!!!
Wow awseome :-)

Filtering Exceptions

2005-12-09T23:24:00.000+03:00

Some languages like VB.NET but not C# supports Exception Filters .

Let's take these quick scenarios :

1- procedure A which has an exception handler is calling Proc B which
doesn't have an exception handler. Proc B Throw an exception . What happens
? Of course the runtime will search the stack for any catch until it hits A.
so A cacth the exception

2- same as before but B has an exception handler . What happens ? Of course
B catch the exception which might in turn voluntarily throw the exception .

3-
Sub A
Try
B()
Catch when Filter1() = True
DoSomething()
End Try
End sub

Function Filter1() as boolean
return True
End function

Sub B
Try
DoWork()
Finally
FinalizeMyWork()
End Try
End sub

Sub DoWork()
throw new exception()
End sub

The question now is : what are the ordered steps of execution ?
1- A calls B
2- B calls DoWork()
3- DoWork throw an exception
4- CLR will search in the stack for a handler until it finds A's
Handler
5- this is the trick . Filter1 is executed
6- B's Finally
7- DoSomething

So here is the lesson : TAKE CARE , some code could run after the try and
before the Finally . In our case , from B's Perspective , DoWork() is
executed then (SHOULD) followed by FinalizeMyWork(). But in practical , NO the
filter is executed in between . For me it is like (not is) code injection .

Throw THINGS that are not exceptions !!!

2005-12-08T18:27:00.000+03:00

This is my first time to know that we can throw types that are not
exceptions (not derived from system.exception)
Fortunately this cannot be done directly from CLS compliant languages like
C# and VB , but what if we are calling method M1() written by naughty C++ or
IL which throws an integer for example (throw 4). How can we catch this in
C# or VB ?

In .NET v1.x we can write :

Try
'call a naughty code that throws a non-exception
Catch

End try

This approach has 2 issues :
1- there is no variable for catching the exception
2- non-system exceptions are not accumulated on the stack trace so we cannot
debug .

In .NET v2.0 :

Non-system exceptions are wrapped up with
System.Runtime.CompilerServices.RuntimeWrappedException which derives from
System.Exception . And even more there is a switch to enable or disable this
: <Assembly:
System.Runtime.CompilerServices.RuntimeCompatibilityAttribute(true)>

CLR Magic :

If assembly A (written in IL) throws a non-system exception . Assembly B
(written in C#) calls A . Assembly C (written in C++) call B.
1- if A catch it . It will see the non-system exception and never see that
it has been wrapped
2- if B catch it . It will see RuntimeWrappedException
3- if C catch it . It will see the non-system exception and never see that
it has been wrapped

Dynamic ports and muli-port/IP listener in SQL 2005

2005-11-25T22:26:00.000+03:00

In the configuration manager , you can configure SQL 2005 to listen on
multiple Ips , and even more you can make it listen to multiple ports on the
same IP (1440,1450,1460) , but in this case you have to make "listen ALL =
NO"

Moreovere you can configure the server to have dynamic port , so when the
service is strating , it asks the OS for an available port, opens an
endpoint for that port.
SQL Server Browser monitors the ports, and direct incoming connections to
the right port for specific instance.
So what happens if SQLBrowser is off ? Of course clients must provide the
right IP and port otherwise they cannot connect.
So sql browser acts as a resolution for instance name to their ports .
The client send a UDP msg to port 1434 with the name of the instance , the
sql browser replies with the port.

The war of SQL vs. Xquery

2005-11-25T18:52:00.000+03:00

The world is your database with Log Parser.

I can think of this as a point towards the relational world against the
hierarchical world ...

http://www.microsoft.com/downloads/details.aspx?FamilyID=890cd06b-abf8-4c25-
91b2-f8d975cf8c07&displaylang=en

Log parser is a powerful, versatile tool that provides universal query
access to text-based data such as log files, XML files and CSV files, as
well as key data sources on the WindowsR operating system such as the Event
Log, the Registry, the file system, and Active DirectoryR. You tell Log
Parser what information you need and how you want it processed. The results
of your query can be custom-formatted in text based output, or they can be
persisted to more specialty targets like SQL, SYSLOG, or a chart.

Most software is designed to accomplish a limited number of specific tasks.
Log Parser is different... the number of ways it can be used is limited only
by the needs and imagination of the user.

Cannot delete fileX :Access is Denied

2005-11-19T12:00:00.000+03:00

How many times did you get this message ?

"Cannot delete fileX :Access is Denied
Make Sure the Disk is not full or write-protected
And the file is not currently in use"

I think a lot ha ?
At last I got a solution from the BCL Team

you can use it to enumerate the processes that are using the blocked module

For example : LMOD.exe file1.dll
Then you get a list of running process who are using file1.dll module

/// <summary>
/// Simple tool to find out which process have loaded a particular module.
/// </summary>
public class LMod
{
// "System Idle Process" pid
static int IdleProcessID = 0;

// "System" pid
static int SystemProcessID
{
get
{
//Is older than XP...
if (Environment.OSVersion.Version.Major < 5 ||
(Environment.OSVersion.Version.Major == 5 &&
Environment.OSVersion.Version.Minor == 0))
return 8;
else
return 4;
}
}
public static int Main(string[] args)
{
int total = 0;
string m_ModuleName = "";

if (args.Length == 1)
m_ModuleName = args[0];
else
{
// wrong number of parameters...
Console.WriteLine("Usage: LMod module_name");
return 1;
}

// Get all running processes on the machine...
Process[] m_arrSysProcesses = Process.GetProcesses();
for (int i = 0; i < m_arrSysProcesses.Length; i++)
{
try
{
ProcessModuleCollection modules =
m_arrSysProcesses[i].Modules;
int nCount = modules.Count;

if (nCount > 0)
{
for (int j = 0; j < nCount; j++)
{
// Is it the module we are looking for?
if (modules[j].ModuleName == m_ModuleName)
{
Console.WriteLine("-------------------");
Console.WriteLine("Process Name: "
+ m_arrSysProcesses[i].ProcessName);
Console.WriteLine("Process ID : "
+ m_arrSysProcesses[i].Id);
Console.WriteLine("Priority : "
+ m_arrSysProcesses[i].BasePriority);
Console.WriteLine("Memory Usage: "
+ (m_arrSysProcesses[i].WorkingSet64 /
1024) + " Kb");
Console.WriteLine();

total++;
break;
}
}
}
}
catch (Exception e)
{
// System Idle Process (Idle): represents pseudo-process
// that represents all the processor time not used by
// other processes.
// System (System): represents the processor time
// used by the kernel itself.
if (m_arrSysProcesses[i].Id != SystemProcessID
&& m_arrSysProcesses[i].Id != IdleProcessID)
{
Console.WriteLine("Error: Process "
+ m_arrSysProcesses[i].ProcessName
+ " (" + m_arrSysProcesses[i].Id + ") failed!");
Console.WriteLine(e);
return 2;
}
}
}

Console.WriteLine();
Console.WriteLine("There are " + total
+ " processes using module " + m_ModuleName);

return 100;
}
}

(Singularity) New MS OS other than Windows

2005-11-12T16:40:00.000+03:00

http://research.microsoft.com/os/singularity/

This is just a little brief about the new OS :

Singularity is a new operating system being developed as a basis for more
dependable
system and application software [28]. Singularity exploits advances in
programming languages
and tools to create an environment in which software is more likely to be
built correctly, program
behavior is easier to verify, and run-time failures can be contained.

A key aspect of Singularity is an extension model based on Software-Isolated
Processes
(SIPs), which encapsulate pieces of an application or a system and provide
information hiding,
failure isolation, and strong interfaces. SIPs are used throughout the
operating system and
application software. We believe that building a system on this abstraction
will lead to more
dependable software.

SIPs are the OS processes on Singularity. All code outside the kernel
executes in a SIP. SIPs
differ from conventional operating system processes in a number of ways:
- SIPs are closed object spaces, not address spaces. Two Singularity
processes cannot
simultaneously access an object. Communications between processes transfers
exclusive
ownership of data.
- SIPs are closed code spaces. A process cannot dynamically load or generate
code.
- SIPs do not rely on memory management hardware for isolation. Multiple
SIPs can reside
in a physical or virtual address space.
- Communications between SIPs is through bidirectional, strongly typed,
higher-order
channels. A channel specifies its communications protocol as well as the
values
transferred, and both aspects are verified.
- SIPs are inexpensive to create and communication between SIPs incurs low
overhead.
Low cost makes it practical to use SIPs as a fine-grain isolation and
extension
mechanism.

- SIPs are created and terminated by the operating system, so that on
termination, a SIP's
resources can be efficiently reclaimed.
- SIPs executed independently, even to the extent of having different data
layouts, run-time
systems, and garbage collectors.

SIPs are not just used to encapsulate application extensions. Singularity
uses a single
mechanism for both protection and extensibility, instead of the conventional
dual mechanisms of
processes and dynamic code loading. As a consequence, Singularity needs only
one error
recovery model, one communication mechanism, one security policy, and one
programming
model, rather than the layers of partially redundant mechanisms and policies
in current systems.
A key experiment in Singularity is to construct an entire operating system
using SIPs and
demonstrate that the resulting system is more dependable than a conventional
system

There are a lot more in the report on the research site

Quartz Web Designer for ASP.NET II from Microsoft

2005-10-17T01:46:00.000+03:00

now we can build a very powerful design model based on WPF which can now target ASP.NET Clients

http://www.microsoft.com/products/expression/en/web_designer/default.aspx

Encrypting web.config without writing Code

2005-10-12T16:52:00.000+03:00

I think alot of people needs to encrypt their web.config sections in an easy way . it has never been easier than ASP.NET 2.0

1- Tool : Aspnet_regiis.exe .

limited to certain kind of sections . there are some system sections like (<processModel>, <runtime>, <system.runtime.remoting> ) that cannot be encrypted using this tool , so we have to use another tool which is Aspnet_setreg.exe .

2- Encryption Provider : RSA

3- key Storage Location : Encryption Keys are saved in Container files

a- Machine Container : the encryption key is shared to all applications running on the same server. ( \Documents and Settings\All Users\Application Data\Microsoft\Crypto\RSA\MachineKeys ).

The shared Encryption key Container : "NetFrameworkConfigurationKey"

b- User Container : the encryption key is only accesible by our application. ( \Documents and Settings\{UserName}\Application Data\Microsoft\Crypto\RSA )

4- Encrypting :

for IIS : aspnet_regiis -pe "ParentSection/ChildSection" -app "/WebApplication1"

-pe : the section to be encrypted like "connectionStrings" or "appSettings/App1"

-app: the virtual path to the application

-pd : for decryption

For the built-in web server with Visual Studio.NET 2005 :
aspnet_regiis.exe -pef "ParentSection/ChildSection" C:\MyWebs\WebApp1

-pef: section to be encrypted + physical path

-pdf: for decryption

For User Container Storage :

The good news is that you dont have to write anything special in your code to read the encrypted data .it is read by the same way : ConfigurationManager.ConnectionStrings("MyConn1").ConnectionString

5- ACL on the Encryption Key : which web application has permission to read encrypted data ?

any ASP.NET Web APP has an identity (in IIS6 , it is the identity of the App Pool). when an ASP.NET web App tried to read encrypted Data , ASP.NET checks if that application has the appropriate permission by checking the NTFS ACL on the Encryption Key Container File (for shared Machine Container it is :NetFrameworkConfigurationKey) against app identity

Access Denied : If your web APP doesnt have permission to access the key --> "Parser Error Message: Failed to decrypt using provider 'RsaProtectedConfigurationProvider'. Error message from the provider: The handle is invalid."

Grant Access to an Account: aspnet_regiis -pa "NetFrameworkConfigurationKey" "MyServer\MyUser"

2005-10-10T11:40:00.000+03:00

App_Offline.htm

very cool feature form ASP.NET II . just place a page in the root of your web app with this file "App_offline.htm" and the server will unload the web app and unload the app domain and stop processing any requestes . it just displays the contents of the htm page. this can be used during maintenance.the only complaint is that you cannot control the name of the page in any config file coz this is executed before loading any config file ...

removing this file from the root will result in immediate normal processing for requests from the next request

2005-10-10T03:35:00.000+03:00

Using the HTTP.SYS Kernel Mode Cache from ASP.NET

first question of course will be "what is the difference between Kernel mode and user mode ?" .

kernel mode is the OS mode .it is by default a 2GB piece of memory. it is a protected area .running under elevated privilages(Local System) . so anything running in kernel mode is actually very very fast over user mode coz they have elevated priority over anything running in User mode .
by default User mode is 2GB peice of memory. it is the place to run all the applications ( including IIS) in windows OS

so one of the implications of implementing a kernel mode http listener is dramatically increase the performance .

let's have a look on caching in ASP.NET Today , I could take the data i need to cache and basically store it in memory and guarantee that on subsequent requests, IIS is going to call ASP.NET; ASP.NET is going to get the choice to say, based on the URL you're asking for, I'm going to fetch this out of memory if I have it; and then I can send a response back down. But with IIS 6.0, the extra benefit you get is that rather than IIS ever having even talked to us, the request can be pushed in IIS and it can be served straight from IIS.

so caching data in kernel mode (HTTP.SYS) avoids context switches between user mode and kernel mode .it is dramatically increasing performance , and when talking about performance we can measure this with a very simple page built with ASP.NET on MS Application Center . the difference between no of req/sec before and after apply caching is incredible

note: to apply HTTP.SYS caching from ASP.NET you have to add the @OutPutCache Directive to the page

2005-10-10T01:59:00.000+03:00

Wiki

i heard alot about wiki i always want to know what is really a wiki .
so languistically speaking : wiki is a huwai'ian keyword which means "Quick"
In Hawai'ian repeated words provide emphasis, so WikiWiki means very quick
That makes a WikiWikiWeb a very quick way to create web-based content.

from a Technical Technical perspective , you can consider a wiki like a dashboard or a white board but instead of only one person writing on it , no there can be multiplie persons from all over the world can be writing on it , and modification to the text on the white board it tracked to his modifier. so it is amix between chatting , collaboration and discussion board .

let's take an example

go to http://www.flexwiki.com/

alomst every page you see from now on is a complete wiki and it is called a topic. for example the first link in the page in the right section is pointing to http://www.flexwiki.com/default.aspx/FlexWiki/WikiWiki.html, please click on it

this opened web page now is a topic using the wiki methodologies

let's say you need to change the page , you need to add your own text on that page or change or delete. simply double click any where on any white space portion on that page

now we are inside wiki editor

change the text freely and please have a look on the right pane, where you can change your contribution change "Name" and change templates and then click save

the previous page is back now but with your change which is exposed to any one in the world. you can try this yourself bu opening the same page now from another computer

for example lets say that i need to track all changes not that has happened to that page, i can simply click on show changes on the left . it will show me all the changes to that page

a very great feature is also the "recent changes" from the left pane , click on that . you can now see all the changes to the current namespace and you can even filter by author. let's filter by my name for example "Hussein". click in the combo box "Authors" and click "H" in the keyboard then down to "Hussein Computer"

so now for any site , we should have a wiki just to post our own comments about the site , these comments might be questions , answers , notes , summary , etc....

2005-09-13T00:26:00.000+03:00

Convert Your .NET Apps to Flash ..........

wowwwwwwwwwwwwwwwwww

no need now for JIT or the whole CLR . i dont know what does MS Says now ?
we can really get rid of all the framework .

http://www.xamlon.com/software/xamlonpro/flash/

a VB.NET 2003 Hall of Shame which is now fixed in 2005

2005-07-24T01:41:00.000+03:00

A new Solution for Another Hall Of Shame

in SQL Server CE v 2.0 . i always get this question more and more and more . "is there any way to work online with SQL CE v 2.0 ?"

unfotunately we cannot use the ADOCE from .NET CF 1.1 since the .NET CF 1.1 doesnt have a COM INTEROP, so the only solution is to use of course the ADO.NET . but what do microsoft enforces us to use an offline behaviour in an online solution . i dont need to work with ADO.NET on .NET CF coz we have a huge number of disadvantages ( HUGE HUGE):
1- Loading a Dataset in Memory is eating the memory and i always get "OutofMemory exception"
2- going to the DataReader is like leaving one problem to a larger one. DataReaders are readonly .
3- i cannot design my DB on the Desktop(unless by a third party tools like SQL CE console) , and this is driving alot of developers to madness.it is very difficult to create a DB and Schema on the Device itself .
4- the SQL CE v 2.0 is very Weak . it doesnt support anything except just plain tables. i cannot have views . i cannot have anything.

and alot more...............................

unfortunately some enterprise solutions i have seen myself is totally built on XML instead of SQL Server CE v 2.0 . i asked the develoeprs there "why?" they said we have alot of functionality beyond that in the SQL CE.
Honestly , the only good things i see in SQL CE v.20 are :
1- Seek method . i have built a solution with a 350,000 records in one table and the seek method has just taken 1 second for returning a specific row in the worst case.
2- compact DB.

and now the real fun begin :

the SQL Mobile :
1- Supports ResultSets so we can now (AT LAST) work online , instead of loading all the Dataset in memory.
2- Multiple connections on the same DB . this was one of the most annoying thing for me .
3- you can design your complete solution and test it on the desktop and then deploy it to the device.

and moreeeeee............

2005-04-14T13:22:00.000+03:00

Centralized Exception handling in Windows Forms :

can we really have a centralized exception management in windows forms apps ?
we always hear this :
1- i need a procedure to be triggered whenever any error in the applciation is fired (may be just to log and trace) without writing try and catch blocks.

in VB.NET :

shared sub main()
AddHandler Application.ThreadException, AddressOf s1
end sub

Sub s1(ByVal sender As Object, ByVal e As Threading.ThreadExceptionEventArgs)
MessageBox.Show("Centralized Exception trapping")
End Sub

in C#.NET :

static void main()
{
Application.ThreadException += new ThreadExceptionEventHandler(Application_ThreadException);
}

private static void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e)
{
MessageBox.Show("Centralized Exception trapping");
}

2005-04-05T23:38:00.000+03:00

Compile of VB Imports vs. C# using

let's look at this Console App written in VB .

Imports System.Data
Imports System.Windows.Forms

Class class1
     Shared Sub Main()
             Console.Writeline("Welcome")
     End Sub
End Class

open the ConsoleApplication1.exe with ILDASM and have a look in manifest . UNFORTUNATELY vb compiler generated IL still references the system.data although it is not used in our app .

FORTUNATELY This is not the case in C#. try the same thing in C# , we find that C# compiler is smart enough to remove the unreferenced dlls from IL .

a point to C# against VB :-)

2005-03-27T17:37:00.000+03:00

Cutting the Chain Of overriding

let's see how to Override a method in VB.NET

Class Parent
Public Overridable Sub Test()
End Sub
End Class

ClassChild
    Inherits Parent
    Public Overrides SubTest()
    End Sub
End Class

ClassMoreChild
    Inherits Child
    Public Overrides Sub Test()
    End Sub
EndClass

so can we cut the chain of permission for overriding the Test() method in Child ( i no more need anyone to be able to Override this method, my behaviour is the ultimate so i need to stop permitting my childs to override me )
we can do this in VB.NET by using NotOverridable so class child can be written like this :
ClassChild
    Inherits Parent
    Public NotOverridable Overrides SubTest()
    End Sub
End Class

so now we get a compilation error in MoreChild . but how can we do this in C# ?
unfortunately it cant be done ............. this is another VB vs C# competetion features ...

SO WHAT exactly is a variable type ?

2005-03-05T19:40:00.000+03:00

I asked Ian Griffiths about "SO WHAT exactly is a variable type" ? i think it is the most important question in .NET . for me this is the most exciting question i have faced during the last 6 years about .NET . what exactly is a variable type ?
let's take an example : String s = "Something " ; so the question is "is the LHS and RHS are both of type string?"
another example : Parent P = new Child (); again the same question "is the type of the LHS is Parent or child ? "

this is Ian Answer (copy of his email) :

There’s one question you asked, which is actually ambiguous:

> So what exactly is the type of the LHS ?

The key to understanding this issue is to understand why that question is ambiguous. And to grasp, that, I ask this question in return:

"What do you mean by ‘the type’?"

There are at least 3 answers to this question that seem reasonable, and which contradict one another:

it’s the type of whatever the variable refers to, so in your examples, the type of ‘s’ is String, and the type of ‘p’ is Child.
It’s the type associated with the named location the variable represents, so ‘s’ would be String, and ‘p’ would be Parent
its type is something else
it does not have a type – in the .NET type system, you cannot define a type that represents what a variable is

To understand why 3 or 4 might even be options, let’s look at why neither 1 nor 2 can be strictly correct.

The interesting thing is that both 1 and 2 are useful ideas – in some situations, one or other of these is the way you will want to look at the code. However, it’s clear that 1 is an approximation because it’s really looking at the type of the thing being referred to rather than the variable itself.

But what’s wrong with 2? Well, let’s consider again your example:

String s = "Someone";

According to both 1 and 2, the type of ‘s’ is String. But it’s easy to prove that this is wrong. The String type is immutable. This is well documented – there’s nothing you can do to a string to change it. All of the methods on String that look like they’re going to change it (Trim, ToUpper etc.) leave the String unmodified, and instead create a new String that is the modified version of the original.

So, we know that String is immutable. If ‘s’ is of type String, then it must also be immutable. But it’s not – this works:

s = "Something";

We can change ‘s’. We can’t change the String it refers to, but we can change ‘s’ so that it refers to a whole new String.

In other words, there are thing we can do to this variable ‘s’ that we cannot do to a String. From this, we have to conclude that ‘s’ is not something of type String. The variable is associated with type String – it is a named location which is only able to hold references to String objects. But the variable itself is not a String.

So if you consider the following two statements:

- This object is of type String
  
  This variable is of type String

it should now be clear that they don’t mean the same thing. If an object is of type String, we mean it’s a thing that is instance of the String class. That’s not what we mean when we say that a variable is of type String – it’s a shorthand for something else. It means that the variable is a thing that is able to hold a reference to a thing that is an instance of the String class.

So variables are associated with a type – it determines what they are able to refer to. But these variables themselves are distinct from the things they refer to. So do the variables themselves have a type?

There’s one case where variables clearly do have a type – and that’s when you’re using value types. Consider this:

int i;

In this case, the variable doesn’t refer to an int. It is an int. The value is the variable. This is true for all value types – when you declare a variable of a value type, that variable is an instance of that type. In these cases, both 1 and 2 above are correct.

So the question I originally posed only really pertains to reference types. And the essence of the question is whether it’s 3 or 4 above – is there something in the type system of .NET that represents the variable itself, whose behaviour is demonstrably different from the behaviour of the type(s) it is able to refer to.

Is that any clearer? I know I’ve still left the question unanswered. But that’s intentional – I’m just trying to make it clear that the answer is not obvious. Do you see the problem now?

Passing Data I/O from data Access Tier

2005-02-28T17:38:00.000+03:00

there are 4 ways to pass data I/O from data access layer .

1- Scalar Values : In this case, the caller does not need to know the structure of the entity. it is the most efficient input because only the necessary data is passed . The main disadvantage of this approach is that changes in the underlying data structure may require a corresponding change in the method signature . If the method signature needs to be altered to take account of a new field for example , all uses of that method must be tracked down and changed.

2- XML Strings : passing data by using a single data structure .By gathering all of the data for a business entity , exchanges between applications become much more efficient because data is not broken into multiple discrete units. another advantage will be that XML can be digested by almost every application . The disadvantage of this technique is : tagged data introduces reduntant information .

3- Datasets :
                    a- has optimistic concurrency issues built in on the contrary to ADO objects .
                    b- can hold collections of data corresponding to individual business entities (implemented as table rows) and are well-adapted to hierarchical data.
                    c- When a method accepts a DataSet as an input type, changes to the DataSet schema do not require changes to the method signature.
                    d- incorporate the advantages of XML formats because they can be quickly serialized and deserialized.
Disadvatages : a- big object in memory resulting in high marshaling costs .

4- Custom Entity Components : are implemented as classes or structs(which has better performance . it is a more flexible dynamic way than datasets . they typically represents the underlying business entities (e.g Employee class representing an Employee ). they can also be serialized as XML . they can be created to avoid the high marshaling costs of datasets while gaining the adv of strong typing .
Disadvantages :
        a- representing these entities in Collection will need creating string typed collection or use the ArrayList , which is not the case in Datasets .
        b- the custom collections or the builtin collections in .NET doesnt represent the heirarchy , in contract to datasets relations and also provide filtering and sorting .
        c- binding to controls . they must implement ICollection to be able to be bounded .

Summary :

I- DataSets are recommended if the application is primarily workingwith large collections of items and needs standard sorting, filtering,and searching capabilities. This is especially true if the data needs toincorporate complex or hierarchical relationships.

II- If the application mainly works with instance data (for example, a single Customer or Project object), custom business entities will normally be the better choice. There is no need for the overhead of DataSets when only one row of data is sufficient for most purposes.

III- In many cases, the time and effort of creating custom business entities will not be worth

Passing a value Type ByVal Tricky Question ?

2005-02-23T14:54:00.000+03:00

this is a small tricky question : ( Very IMP )

what is the Console.WriteLine going to print ?

public class Reference public struct Value

{ {

public int i; public int i; //Not Private

public int Prop public int Prop

{ {

get {return i;} get {return i;}

set {i = value;} set {i = value;}

} }

classExample

{

private Reference_r; // Reference type

private Value_v; // Value type

public Example()

{

_r = new Reference();

_v = new Value();

}

public Reference RefProp

{

get {return _r;}

set {_r = value;}

}

public Value ValueProp

{

get {return _v;}

set {_v = value; }

}

class Program

{

static void Main(string[] args)

{

Example e = new Example();

e.ValueProp.i = 4;

Console.WriteLine(e.ValueProp.i); // what is going to be printed after this line ?

}

take care of the line : e.ValueProp.i = 4;

let's divide this line , e.ValueProp is going to return an instance of the Value Struct , then we go ahead and change the "i" field on this struct

so first part is getting the Value instance from the ValueProp :

Value v1 = e.ValueProp; //is V1 is going to take a copy of the returned Value instance or going to reference this instance ?

// of course it is going to take a copy . coz this is a value type byVal assignment

v1.i = 4; //is going to change the "i" field on the copied Instance not the original . so the Console.WriteLine should Print 0

// but the Compiler detects this issue and throw a compile error .

Why Do We have Different exception Classes ?

2005-02-22T19:04:00.000+03:00

i still get the same question frequently . why do we have more than 1 exception class ?

isnt it enough to write code like this :

try {

// protected Code}

catch (Exception ex)

{ // switch (ex) and handle each exception separately }

the exception class will catch all kind of exceptions . and we can internally handle each exception separately .

no , this is not enough , why ?

let's take this sample

try {System.IO.File.Delete("z:\filenotfound.txt");}

catch (exception ex) { //what can we do here if we need to know the name of the file which is not found ?}

so there must be some "Data" about the kind of exception taking place , in our case the name of the file .so that's why we have FileNotFoundException . so it is much more convinient to write something like this :

try {System.IO.File.Delete("z:\filenotfound.txt");}

catch (FileNotFoundException ex) { Console.Writeline(ex.FileName);}

another example will be the ArgumentOutOfRangeException : we need to know the original value of the argument which is out of range .

try {//cause some argument out of range error;}

catch (ArgumentOutOfRangeException ex) { Console.Writeline(ex.ActualValue);}

VS 2005 :

so what is new in 2005 . in VS 2005 we have all the exception classes having a new property which is : Data , that contains all the information available about this error . it looks like the event model of .NET where Microsoft encapsulates all the information about any event in the second parameter of the event "EventArgs e". so now we have "Exception.Data"

Why do we have 2 Comaprison Operators in VB ?

2005-02-16T16:23:00.000+03:00

the 2 comparison operators i am talking about here are : "Is" and "="

actually , the existence of both of them returns to the old VB6 . coz for old classes we used to have 3 property accessors : "Let , get and set " and the old mistake "default properties "

so we can say simply in VB6 :

Label1 = "User Name : " which means Let Label1 = "User Name : "

and we can also say

Label1 = new Label() which means Set Label1 = new label()

so in the past if we say :

if label1 = "User name" then 'do something this is a using of the opreator "="

but if we say if Label1 = label2 then 'do something this invokes the "Is" operator .

we no more have "set" in VB.NET , so some people think "Is" should have been removed from the language as well and have only 1 comparison .

but it is due to simplicity and more readability (from my point of view) that they still keep the "Is" so we still have reference comaprison as well as value comparison or else we are going to write it as the other languages Object.ReferenceEquals(a,b) . so using "Is" is much more readable and cleaner ..

Another Hall Of Shame

2005-02-15T17:34:00.000+03:00

Constructor for ArgumentNullException

public ArgumentNullException( string paramName, string message)

Constructor for ArgumentException

public ArgumentException( string message, string paramName)

ArgumentNullException does not follow the constructor pattern

Installing the msn Toolbar beta on windows 2003 Server

2005-02-14T14:29:00.000+03:00

msiexec /i MsnToolbarSuite.msi TBSDEVCODE=1

unboxing in VB is different than C#

2005-02-13T18:58:00.000+03:00

another point for VB against C#

let's do this example :

in C# :

int i = 7;

object myObj;

myObj = (object)i; //boxing

long j = (long)o; //InvalidCastException

the CLR will only let you convert it back to Integer

in VB :

Dim i As Integer = 4

Dim myobj As Object

myobj = i 'boxing

Dim j As Long = CType(myobj, Long) 'unboxing works fine

'However

Dim k as long = DirectCast (myobj, Long) 'Generates an error coz DirectCast Bypass VB Helper Funs

How is Works :

To make this work, the compiler emits a conversion from Object as a call to a helper function. The helper function takes the Object, looks at the type of the value contained in it and then does the appropriate conversion to the target type. this means an extra step . it might be an extra step in the wrong direction in case i know the returned type , so i will only lose some performace.

so the Rule is : if i know the result TYPE i would use DirectCast which bypasses the VB helper functions , and i get some performance gain .

as you see , the Default is the helper funs , so the language by default (cint , clong , ctype , etc ... ) can unbox to any type unless you need to switch off this nice feature using DirectCast .

this means that , it is not possible to express all VB language in IL . there are some helper functions like Late Binding ( i will take about this later in coming post) which is not found in IL . that's why we need Microsoft.visualbasic.dll in all the VB projects and we cannot remove that reference .

at Last i found Why don't I get an exception when I divide by zero in VB.NET?

2005-02-12T22:15:00.000+03:00

of course not everyone will like this explanation coz it is deep technical , but this is the Man Behind VB.NET reply to that question

While talking about exception handling, Roy ran up against a change in behavior from VB6 to VB.NET. In VB6, if you evaluate the expression "x = x / 0", you'll immediately get a divide by zero exception. In VB.NET, if you evaluate the same expression, no exception is thrown. Instead the value of x is now NaN, also known as "Not a Number." In reality, you could get this behavior in VB6 as well - on the Compile tab of the project properties, there's an "Advanced Optimizations" button that includes an option "Remove Floating Point Error Checks." If you check that and make an exe (it doesn't affect F5 in the IDE), then the assignment will work and x will contain the value NaN.

The reason for all this is that floating point numbers (as defined by the IEEE) support a number of special values that aren't usually surfaced to VB programmers. In addition to NaN, a floating point variable can also contain the values positive and negative infinity. Not being a numerical expert, I won't even pretend to explain what these values are for or why the IEEE felt they were important to include as part of the definition of floating point numbers. The bottom line is that they are there. By default in VB6, though, we inserted X86 instructions that checked for the various non-numerical states and would throw an exception if you encountered one. In VB.NET, however, things were complicated by the way that the CLR IL was designed, namely the fact that it doesn't support a really efficient way to check for non-numerical results. In VB 2002, we tried simulating the VB6 behavior by emitting CKFINITE opcodes after each floating point operation, but this absolutely tanked all floating point performance. So we ended up dropping the VB6 behavior, and now floating point division by zero will result in NaN instead of an exception.

A related issue is that most processors' FPU registers can handle floating point numbers with a higher precision than can be stored in the standard .NET Double datatype. As a result, depending on how the CLR JIT compiler enregisters variables and temporary values, it's possible that floating point operations (including comparisons) can be done at differing levels of precision. For example, the following code could print "False" instead of "True":


Dim d1, d2 As Double

d1 = Atn(-1)
d2 = Atn(-1)

If d1 = d2 Then
    Console.WriteLine("True")
Else
    Console.WriteLine("False")
End If

That's because one of the variables could be left in a FPU register while the other variable is actually stored back on the stack. When you compare the two values, they aren't equal because one of the values was truncated (so it could be stored on the stack) and the other value wasn't. By default, VB6 suppressed this behavior by emitting X86 code to truncate values that were at higher precisions. (You can turn this off on the advanced optimizations page, too, under the option "Allow Unrounded Floating Point Operations.") But the CLR equivalent - inserting CONV.R8 opcodes everywhere a higher precision value might be used - had similar performance problems to the NaN checks.

As a result, VB.NET floating point operations are much "closer to the metal," which is either a good thing or a bad thing depending on your perspective. You definitely have to be a little more aware of what you're doing when dealing with floating point numbers...

In a response to my previous entry, Cory asks:

...how would you solve the comparison of two values if one is still on the stack and the other has been [stored in a register]? In other words, what would be the proper way to handle this type of situation (work around, etc.)?

A good question, and one that I should have addressed. You can get the compiler to insert explicit CONV.R8 opcodes by using the CDbl() conversion operator. So the code example would look like:


Dim d1, d2 As Double

d1 = Atn(-1)
d2 = Atn(-1)

If CDbl(d1) = CDbl(d2) Then
    Console.WriteLine("True")
Else
    Console.WriteLine("False")
End If

If you look at the code this compiles to, you should see CONV.R8 opcodes after each local is loaded, and that should force the values to both be truncated

Can We turn OFF the background compilation for VB

2005-02-12T18:00:00.000+03:00

no we cannot do that . there were many requests for that in VB 2002 coz huge projects were slow , but this was solved in 2003 . the main reason why MS cannot give a switch to turn off this feature is :

The information provided by background compilation drives Intellisense, it enables the WinForms designer (as well as all other designers), it fills the dropdowns at the top of the window, it drives the object browser, it enables go to definition, etc, etc, etc. Essentially, without background compilation, the IDE becomes Notepad.exe with syntax coloring. (Coloring, interestingly enough, does not require background compilation because it's entirely based off the lexical grammar of the language and requires no further knowledge of the code.)

another Point for VB against C#

2005-02-12T17:35:00.000+03:00

this is another VB vs C# thing :

some people say : Given VBA's long history with Office, one might expect VB .NET to be the primary language among .NET developers using Office as a platform. But I've seen a lot of evidence that C# usage of Visual Studio Tools for Office (aka VSTO) is high.

so programming against Office is one of those places where VB has got it over C# hands-down

1- C# can’t bind to Word’s Close event and VB can

in C# we cannot have :

private void ThisDocument_CloseEvent()

{

}

while in VB we have :

Private Sub ThisDocument_CloseEvent() Handles Me.CloseEvent

End Sub

2- printing a word document , since VB Supports named Arguments , :

in VB : Doc.PrintOut(Copies := 2, Collate := true)

in C# :

object copies = 2;
object collate = true;
Doc.PrintOut(ref missing, ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing, ref copies,
ref missing, ref missing, ref missing, ref collate,
ref missing, ref missing, ref missing, ref missing,
ref missing, ref missing);

msn search

2005-02-01T22:15:00.000+03:00

now you can search any where

http://www.imagine-msn.com/search/tour/desktop.aspx