Wednesday, February 23, 2005
Passing a value Type ByVal Tricky Question ?
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
SO
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 .
: 7:11 PM << Home
