Question

In VB.NET, what is the difference between And and AndAlso? Which should I use?

Answer 1

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/