IsNothing versus Is Nothing

Question

Does anyone here use VB.NET and have a strong preference for or against using IsNothing as opposed to Is Nothing (for example, If IsNothing(a

Answer 1

You should absolutely avoid using IsNothing()

Here are 4 reasons from the article IsNothing() VS Is Nothing

1. Most importantly, IsNothing(object) has everything passed to it as an object, even value types! Since value types cannot be Nothing, it’s a completely wasted check.
   Take the following example:

   Dim i As Integer
   If IsNothing(i) Then
      ' Do something 
   End If
   

   This will compile and run fine, whereas this:

   Dim i As Integer
   If i Is Nothing Then
       '   Do something 
   End If
   

   Will not compile, instead the compiler will raise the error:

   'Is' operator does not accept operands of type 'Integer'.
   Operands must be reference or nullable types.

2. IsNothing(object) is actually part of part of the Microsoft.VisualBasic.dll.
   This is undesirable as you have an unneeded dependency on the VisualBasic library.

3. Its slow - 33.76% slower in fact (over 1000000000 iterations)!

4. Perhaps personal preference, but IsNothing() reads like a Yoda Condition. When you look at a variable you're checking it's state, with it as the subject of your investigation.

   i.e. does it do x? --- NOT Is xing a property of it?

   So I think If a IsNot Nothing reads better than If Not IsNothing(a)