VB.Net Logical Operations and drag/drop flags

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Recently I got some email about how some of the VB.Net code I posted on the drag/drop series should translate to C#, specifically about these fragments.

If (e.AllowedEffects And DragDropEffects.Copy) = 0 AndAlso _
(e.AllowedEffects And DragDropEffects.Move) = 0 Then
e.Effects = DragDropEffects.None
Return False
End If

' Figure out whether we should copy or move. If we can do either, we'll move unless
' Ctrl is pressed.
If (e.AllowedEffects And DragDropEffects.Copy) <> 0 AndAlso _
(e.AllowedEffects And DragDropEffects.Move) <> 0 Then
If (e.KeyStates And DragDropKeyStates.ControlKey) <> 0 Then
e.Effects = DragDropEffects.Copy
...

And is the bitwise & operator. Read this for more information.

In the first snippet, typically AllowedEffects will be one or more of Copy, Move and Link (DragDropEffect values are used as flags). I only handle Copy and Move, so if neither of them is set, I bail out in the first check.

In the second snippet, if I can Copy and Move the item, I’ll have to pick one. I decided to go with Move by default, and allow the user to toggle this behavior by using the control key.

 

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