Change content of a List<T>?

[Gary]

I am using List<MyClassto store a bunch of MyClasses. And in my program, I
want to change the content of one class in this list. However, it seems to me
that this list keeps an original copy and is only "readable".

Following is my code:

int index = GetMyClassIndFr omName(string);

if (index != -1)
{
MyClass mf = m_allMyClass[index];
mf.Available = true;
}

I think the mf is just a temporary copy of that MyClass. How may I change
the original content?

Thanks,

[Peter Bromberg [C# MVP]]

Gary,
Let's clear this up with a handy-dandy little console app you can run:

using System;
using System.Collecti ons.Generic;
using System.Text;
namespace ListMyClass
{
public class MyClass
{
public int Id;
public string Name;
public MyClass(int id, string name)
{
this.Id = id;
this.Name = name;
}
}
class Program
{
static void Main(string[] args)
{
List<MyClassmyC lasses= new List<MyClass>() ;
myClasses.Add(n ew MyClass(1, "Testing1") );
myClasses.Add(n ew MyClass(2, "Testing2") );
MyClass test = myClasses[0];
test.Name = "BORK!";
test.Id = 1229;
MyClass test2 = myClasses[0];
Console.WriteLi ne(test2.Id.ToS tring() + ": " + test2.Name);
Console.ReadLin e();
}
}
}

--Enjoy.
Peter
--
Co-founder, Eggheadcafe.com developer portal:
http://www.eggheadcafe.com
UnBlog:
http://petesbloggerama.blogspot.com


"Gary" wrote:

I am using List<MyClassto store a bunch of MyClasses. And in my program, I
want to change the content of one class in this list. However, it seems to me
that this list keeps an original copy and is only "readable".

Following is my code:

int index = GetMyClassIndFr omName(string);

if (index != -1)
{
MyClass mf = m_allMyClass[index];
mf.Available = true;
}

I think the mf is just a temporary copy of that MyClass. How may I change
the original content?

Thanks,

[Stoitcho Goutsev \(100\)]

Gary,

Is by any chance MyClass decalred as a structure?
Otherwise there is no reason to get a copy of the actual value.

Can you post a simple, compilable sample that demonstrates the problem?
--
Stoitcho Goutsev (100)

"Gary" <Ga**@discussio ns.microsoft.co mwrote in message
news:BE******** *************** ***********@mic rosoft.com...

>I am using List<MyClassto store a bunch of MyClasses. And in my program,
I
want to change the content of one class in this list. However, it seems to
me
that this list keeps an original copy and is only "readable".

Following is my code:

int index = GetMyClassIndFr omName(string);

if (index != -1)
{
MyClass mf = m_allMyClass[index];
mf.Available = true;
}

I think the mf is just a temporary copy of that MyClass. How may I change
the original content?

Thanks,

[Gary]

Yes. It is a structure actually. I believe that caused the problem.

Thanks,

"Stoitcho Goutsev (100)" wrote:

Gary,

Is by any chance MyClass decalred as a structure?
Otherwise there is no reason to get a copy of the actual value.

Can you post a simple, compilable sample that demonstrates the problem?
--
Stoitcho Goutsev (100)

"Gary" <Ga**@discussio ns.microsoft.co mwrote in message
news:BE******** *************** ***********@mic rosoft.com...

I am using List<MyClassto store a bunch of MyClasses. And in my program,
I
want to change the content of one class in this list. However, it seems to
me
that this list keeps an original copy and is only "readable".

Following is my code:

int index = GetMyClassIndFr omName(string);

if (index != -1)
{
MyClass mf = m_allMyClass[index];
mf.Available = true;
}

I think the mf is just a temporary copy of that MyClass. How may I change
the original content?

Thanks,

[Stoitcho Goutsev \(100\)]

Yes, value types are always copied.
--
HTH
Stoitcho Goutsev (100)

"Gary" <Ga**@discussio ns.microsoft.co mwrote in message
news:CD******** *************** ***********@mic rosoft.com...

Yes. It is a structure actually. I believe that caused the problem.

Thanks,

"Stoitcho Goutsev (100)" wrote:

>Gary,

Is by any chance MyClass decalred as a structure?
Otherwise there is no reason to get a copy of the actual value.

Can you post a simple, compilable sample that demonstrates the problem?
--
Stoitcho Goutsev (100)

"Gary" <Ga**@discussio ns.microsoft.co mwrote in message
news:BE******* *************** ************@mi crosoft.com...

>I am using List<MyClassto store a bunch of MyClasses. And in my
program,
I
want to change the content of one class in this list. However, it seems
to
me
that this list keeps an original copy and is only "readable".

Following is my code:

int index = GetMyClassIndFr omName(string);

if (index != -1)
{
MyClass mf = m_allMyClass[index];
mf.Available = true;
}

I think the mf is just a temporary copy of that MyClass. How may I
change
the original content?

Thanks,

[Joanna Carter [TeamB]]

"Gary" <Ga**@discussio ns.microsoft.co ma écrit dans le message de news:
BE************* *************** **...icrosof t.com...

|I am using List<MyClassto store a bunch of MyClasses. And in my program,
I
| want to change the content of one class in this list. However, it seems to
me
| that this list keeps an original copy and is only "readable".
|
| Following is my code:
|
| int index = GetMyClassIndFr omName(string);
|
| if (index != -1)
| {
| MyClass mf = m_allMyClass[index];
| mf.Available = true;
| }
|
| I think the mf is just a temporary copy of that MyClass. How may I change
| the original content?

No, mf is just another reference to the same object held in the list. So if
you change the properties of mf, you will also see those changes in the
properties of the object in the list; as they are one and the same object.

Joanna

--
Joanna Carter [TeamB]
Consultant Software Engineer