Problem compiling new VB.Net class

[nzmike]

Hi all,

I have a VB.Net app that uses a ListView object. Since I want to be able to sort the columns of the ListView by clicking on the column headers I decided to write/plunder(!) a class to do this. I hunted around on the net first to get an idea how to do it and found a class (in C#) which I decided to convert.

I've done the conversion from C# to VB.Net but am getting one really stubborn error that I can't solve. The error I'm getting from the class (listed below) is this:

E:\VS.NET\Projects\BatchRename\ListViewSortManager.vb(21): 'BatchRename.MJC.Windows.Forms.ListViewTextSort' must implement 'Overridable Overloads Function Compare(x As Object, y As Object) As Integer' for interface 'System.Collections.IComparer'.

The thing is I *am* implementing Compare in my class - exactly how VS.Net tells me it wants it!

Here's the code...

Public Class ListViewTextSort
Implements IComparer

Private m_column As Integer
Private m_ascending As Boolean

'Constructor
Public Sub New(ByVal column As Integer, ByVal ascending As Boolean)
m_column = column
m_ascending = ascending
End Sub

'Implementation of IComparer.Compare
Overridable Overloads Function Compare(ByVal lhs As Object, ByVal rhs As Object) As Integer

Dim lhsLvi As ListViewItem = CType(lhs, ListViewItem)
Dim rhsLvi As ListViewItem = CType(rhs, ListViewItem)

If lhsLvi Is Nothing Or rhsLvi Is Nothing Then
Return 0
End If

Dim lhsItems As ListViewItem.ListViewSubItemCollection = lhsLvi.SubItems
Dim rhsItems As ListViewItem.ListViewSubItemCollection = rhsLvi.SubItems

Dim lhsText As String
Dim rhsText As String

If lhsItems.Count > m_column Then
lhsText = lhsItems(m_column).Text
Else
lhsText = String.Empty
End If

If rhsItems.Count > m_column Then
rhsText = rhsItems(m_column).Text
Else
rhsText = String.Empty
End If

Dim result As Integer = 0

If lhsText.Length = 0 Or rhsText.Length = 0 Then
result = lhsText.CompareTo(rhsText)
Else
result = OnCompare(lhsText, rhsText)
End If

If Not m_ascending Then
result = -result
End If

Return result

End Function


'Overridden to do type-specific comparision.
Protected Overridable Function OnCompare(ByVal lhs As String, ByVal rhs As String) As Integer

Return String.Compare(lhs, rhs, False)

End Function


End Class


I'm really no OO expert - can anybody spot what the problem might be here?

TIA...

Mike.

[Edneeis]

You listed it as Implementing IComparer but didn't implement the methods that are required. Change this:
Protected Overridable Function OnCompare(ByVal lhs As String, ByVal rhs As String) As Integer

To this:
Protected Overridable Function OnCompare(ByVal lhs As String, ByVal rhs As String) As Integer Implements IComparer.OnCompare

[nzmike]

Thanks for that - I added the "Implements IComparer.OnCompare" to the end of it and solved the problem!!

Mike.