error very strange

[Argentino Douglas]

a function, whose parameter is a ref to a collection of class I
private void func(List<I> i){
for(int n=0;n<MAXVALUE;++n){

for(int m=0;m<MAXVALUE;++m){

Dosomething();
}

i[n].value=5; [******]Eror: can't modify the value of
System.Collections.Generic.List<program.Form1.I>.this[int] because it
is not a variable[/******]
}


Thanks

 

[Argentino Douglas]

Any questions or answers ? Looks like nobody is in now.

 

[Jon Skeet [C# MVP]]

a function, whose parameter is a ref to a collection of class I
private void func(List<I> i){
for(int n=0;n<MAXVALUE;++n){

for(int m=0;m<MAXVALUE;++m){

Dosomething();
}

i[n].value=5; [******]Eror: can't modify the value of
System.Collections.Generic.List<program.Form1.I>.this[int] because it
is not a variable[/******]
}

Could you post a short but complete program which demonstrates the
problem?

See http://www.pobox.com/~skeet/csharp/complete.html for details of
what I mean by that.

 

[Argentino Douglas]

public struct I{
public int value;
}

private void ValuableHelper(List<I>i){

i=new List<I>();

for(int n=0;n<MAXVALUE;++n){

for(int m=0;m<MAXVALUE;++m){

PleaseHelpMe();

}

i[n].value=5; //Error is here

}
}
I am coding it as a window application,
Thanks

a function, whose parameter is a ref to a collection of class I
private void func(List<I> i){
for(int n=0;n<MAXVALUE;++n){

for(int m=0;m<MAXVALUE;++m){

Dosomething();
}

i[n].value=5; [******]Eror: can't modify the value of
System.Collections.Generic.List<program.Form1.I>.this[int] because it
is not a variable[/******]
}

Could you post a short but complete program which demonstrates the
problem?

See http://www.pobox.com/~skeet/csharp/complete.html for details of
what I mean by that.

 

[Jon Skeet [C# MVP]]

public struct I{
public int value;
}

private void ValuableHelper(List<I>i){

i=new List<I>();

for(int n=0;n<MAXVALUE;++n){

for(int m=0;m<MAXVALUE;++m){

PleaseHelpMe();

}

i[n].value=5; //Error is here

}
}
I am coding it as a window application,

Well, firstly, that's *not* a short but complete program. Please read
http://www.pobox.com/~skeet/csharp/incomplete.html

However, the cause of your problem is that you've got a struct - a
value type - and you're trying to change a value which is returned from
an indexer. You can't do that, and even if you did, it wouldn't do what
you wanted it to.

i[n] returns a value. If you modify that value, it won't change the
contents of the list at all.

Now, if I were a reference type, you'd be modifying the value *referred
to* by the reference in the list, and that would be a different matter.

This kind of problem is just one reason why mutable value types are
generally a bad idea.

Oh, and regards your other post: you can't expect replies *that*
quickly. You only left your original message for 9 minutes before
posting again!