ArrayList problem

[leazfe]

I have used an arrayList in order to avoid te capacity problems. But, i am getting the next error when i try to iterate over all elements:

An unhandled exception of type 'System.InvalidOperationException' occurred in mscorlib.dll
Additional information: Collection was modified; enumeration operation may not execute.

The code is:

For Each tmpTree In ar
    If tmpTree.IsLeaf Then
       ar.Remove(tmpTree)
    End If
Next

The Message is enought clear, but really am I not able to modifie the arraylist?

Thanks,
Álvaro