Problem with ListViewItemCol lection 'Contains' method

[Piotr Szukalski]

Hi!

I have trouble with 'Contains' method in ListViewItemCol lection class - it
seems like it nevers calls 'Equals' method of class inherited from
ListViewItem... I've found that ListViewItem doesn't override 'Equals'
method, but I _DO_ override it in my class. Have a look at thread:
http://groups.google.com/group/micro...351591db8d07c5

.... and at this piece of code:

using System;
using System.Collecti ons;
using System.Windows. Forms;

namespace CollectionsTest
{
class Class1
{
[STAThread]
static void Main(string[] args)
{
ArrayList ar = new ArrayList();
ar.Add(new MyClass("1"));
ar.Add(new MyClass("2"));

ListView.ListVi ewItemCollectio n col = new ListView.ListVi ewItemCollectio n(new ListView());
col.Add(new MyClass("1"));
col.Add(new MyClass("2"));

System.Console. WriteLine("Cont ains: {0}", ar.Contains(new MyClass("1")));
System.Console. WriteLine("Cont ains: {0}", col.Contains(ne w MyClass("1")));
System.Console. ReadLine();
}
}

class MyClass : System.Windows. Forms.ListViewI tem
{
private string str;

public MyClass(string s)
{
str = s;
}

public override bool Equals(object obj)
{
return str.Equals(obj. ToString());
}

public override int GetHashCode()
{
return str.GetHashCode ();
}

public override string ToString()
{
return str;
}
}
}

ArrayList do calls my 'Equals' method, but ListViewItemsCo llection don't.
Any ideas?

Cheers,
Piotrek

[Jakob Christensen]

ListViewItemCol lection.Contain s does the equivalent of calling
Object.Referenc eEquals when comparing an item to the items in the list, so it
does not call Object.Equals. This means that ListViewItemCol lection.Contain s
only compares references. You will have to implement your own comparison if
you consider two items with the same data to be equivalent.

HTH, Jakob.
--
http://www.dotninjas.dk
http://www.powerbytes.dk
"Piotr Szukalski" wrote:

Hi!

I have trouble with 'Contains' method in ListViewItemCol lection class - it
seems like it nevers calls 'Equals' method of class inherited from
ListViewItem... I've found that ListViewItem doesn't override 'Equals'
method, but I _DO_ override it in my class. Have a look at thread:
http://groups.google.com/group/micro...351591db8d07c5

.... and at this piece of code:

using System;
using System.Collecti ons;
using System.Windows. Forms;

namespace CollectionsTest
{
class Class1
{
[STAThread]
static void Main(string[] args)
{
ArrayList ar = new ArrayList();
ar.Add(new MyClass("1"));
ar.Add(new MyClass("2"));

ListView.ListVi ewItemCollectio n col = new ListView.ListVi ewItemCollectio n(new ListView());
col.Add(new MyClass("1"));
col.Add(new MyClass("2"));

System.Console. WriteLine("Cont ains: {0}", ar.Contains(new MyClass("1")));
System.Console. WriteLine("Cont ains: {0}", col.Contains(ne w MyClass("1")));
System.Console. ReadLine();
}
}

class MyClass : System.Windows. Forms.ListViewI tem
{
private string str;

public MyClass(string s)
{
str = s;
}

public override bool Equals(object obj)
{
return str.Equals(obj. ToString());
}

public override int GetHashCode()
{
return str.GetHashCode ();
}

public override string ToString()
{
return str;
}
}
}

ArrayList do calls my 'Equals' method, but ListViewItemsCo llection don't.
Any ideas?

Cheers,
Piotrek

[Piotr Szukalski]

Hi!

ListViewItemCol lection.Contain s does the equivalent of calling
Object.Referenc eEquals when comparing an item to the items in the list, so it
does not call Object.Equals. This means that ListViewItemCol lection.Contain s
only compares references. You will have to implement your own comparison if
you consider two items with the same data to be equivalent.

Thanks for your answer. I still consider it strange that one
implementation of IList works one way and another seems to follow other
rules... Well, I'm not M$ to make the law... However I wish to find such
information in docs, because it took a while to find bug in my code.

Many thanks,
Piotrek