It seems easier than it is… looping through an array of items (collection) and removing items you don’t want.  However, when you remove an item from a collection while looping through it, the size of the collection changes and the loop may fail… depending on how you are looping.

The correct way to loop through a collection is to essentially loop through it backwards, starting with the item with the maximum ID and working down to zero:

    1  For i As Integer = MyList.Count - 1 To 0 Step -1
    2      If MyList.Items(i).Value <> SomeValue Then
    3          MyList.Remove(MyList(i))
    4      End If
    5  Next