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Old February 6th, 2006, 02:25 AM
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Default IComparer implementation

Hi again folks,

I'm trying to convert an IComparer implementation for a SortedList from VB.NET to C#:

The VB.NET works fine, the C# throws an InvalidCastException where noted in the code. Any idea why?

VB.NET code

Private m_XPanderComparer As XPanderComparer
Private m_ControlList As New SortedList(m_XPanderComparer)


‘ Add control to control list
e.Control.Tag = m_NextControlKey
m_NextControlKey += 1
m_ControlList.Add(e.Control.Tag, e.Control)

‘ VB.NET IComparer implmementation
Public Class XPanderComparer
    Implements IComparer

    Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer Implements System.Collections.IComparer.Compare
        Dim xp1 As XPander = CType(x, XPander)
        Dim xp2 As XPander = CType(y, XPander)
        Dim result As Integer = 0

        If xp1.Top < xp2.Top Then result = -1
        If xp1.Top > xp2.Top Then result = 1

        Return result
    End Function
End Class
C# Code

private XpanderComparer _xpanderComparer = new XpanderComparer();
private SortedList _controlList;


// Add control to control list
e.Control.Tag = _nextControlKey;
_nextControlKey += 1;
_controlList.Add( e.Control.Tag, e.Control );

// C# IComparer implementation
public class XpanderComparer : IComparer

    #region IComparer Members

    public int Compare(object x, object y) 
        XpanderControl xpander1 = (XpanderControl)x; <=== InvalidCastException
    XpanderControl xpander2 = (XpanderControl)y;
    int result = 0;

    if( xpander1.Top < xpander2.Top )
        result = -1;
    if( xpander1.Top > xpander2.Top )
        result = 1;

    return result;

    catch (Exception e) 
        return 0;


Thanks for any thoughts


Old February 6th, 2006, 02:28 AM
Friend of Wrox
Join Date: Jun 2003
Posts: 1,093
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Thanked 12 Times in 11 Posts

Forgot the C# SortedList constructor:

public XpanderListControl () {

    _controlList = new SortedList( _xpanderComparer );



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