Question

Does anyone here use VB.NET and have a strong preference for or against using Not foo Is Nothing as opposed to foo IsNot Nothing? If so, why?

For Example

If var1 IsNot Nothing Then
...
End If

and

If Not var1 Is Nothing Then
...
End If

I just want to know which one is better?
Are they both equally acceptable?

Was it helpful?

Solution

The

If Not var1 Is Nothing Then

Is a hangover from VB6. There didn't used to be an IsNot, and so this was the only way to determine if a variable was not Nothing. It seems to be redundant in VB.NET.

OTHER TIPS

foo IsNot Nothing

The following line is straight from Microsoft's Visual Basic Coding Conventions:

Use the IsNot keyword instead of Not...Is Nothing.

I would go with the first variant - it reads like English and is easier to follow/understand than the second one. Other than that, they are equivalent.

I found a similar question here VB.NET - IsNothing versus Is Nothing, where I feel this question was exhaustively answered. Among the answers Jack Snipes identified http://weblogs.asp.net/psteele/410336, a blog that gives some extra detail. From those I prefer and have used

IsNot Nothing

which also makes my code easier to read and understand.

Using VB 7.0

If var1 Is Not Nothing Then

generates an "invalid use of object error" as per this "VBForums" link.

If var1 IsNot Nothing Then

generates a "Compile error: Expected: Then or GoTo"

If Not IsNothing(var1) Then

worked like a champ

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