Question

I would like to define Sorted to be of type ErrorProviderMessageCollection, which is what unsortedCollection is defined as.

Dim Sorted As ErrorProviderMessageCollection = From item In unsortedCollection 
                                               Order By item.Control.TabIndex

How do I do this?

Public Class ErrorProviderMessage Implements IComparable(Of ErrorProviderMessage)

    Private _Message As String
    Private _Control As Control

    Public Sub New(ByVal message As String, ByVal control As Control)
        _Message = message
        _Control = control
    End Sub

    Public ReadOnly Property Message() As String
        Get
            Return _Message
        End Get
    End Property

    Public ReadOnly Property Control() As Control
        Get
            Return _Control
        End Get
    End Property

    Public Function CompareTo(ByVal other As ErrorProviderMessage) As Integer Implements System.IComparable(Of ErrorProviderMessage).CompareTo
        Return Me.Control.TabIndex.CompareTo(other.Control.TabIndex)
    End Function

End Class

Public Class ErrorProviderMessageCollection

    Inherits System.Collections.ObjectModel.Collection(Of ErrorProviderMessage)

End Class

Answer 1

You could also use Lambda and an appropriate extension method to deal with the casting e.g:

var Sorted = unsortedCollection.OrderBy(i=>i.Control.TabIndex).ToSortedErrorProviderMessageCollection();

and the extension method…

public static class ErrorProviderMessageCollectionHelper
{
    public static ErrorProviderMessageCollection ToSortedErrorProviderMessageCollection <T>(this IEnumerable<T> source) where T : ErrorProviderMessage 
    {
        var orderedCollection = new ErrorProviderMessageCollection();
        foreach (var item in source)
        {
            orderedCollection.Add(item);
        }
        return orderedCollection;
    }
} 

I’m not up on VB.NET so provide the code example in C#.