The And
operator evaluates both sides, where AndAlso
evaluates the right side if and only if the left side is true.
An example:
If mystring IsNot Nothing And mystring.Contains("Foo") Then
' bla bla
End If
The above throws an exception if mystring = Nothing
If mystring IsNot Nothing AndAlso mystring.Contains("Foo") Then
' bla bla
End If
This one does not throw an exception.
So if you come from the C# world, you should use AndAlso
like you would use &&
.
More info here: http://www.panopticoncentral.net/2003/08/18/the-ballad-of-andalso-and-orelse/