What is the difference between 'foo = Nothing' and 'foo is Nothing' in VB.NET?

Question

In VB.NET, what is the difference between

if foo is Nothing Then
      doStuff()
End If

and

if foo=Nothing Then
    doStuff         


        

Answer 1

Asume:

MyFunc(Foo as object)

Foo - Boxed if ValueType

if foo is Nothing Then

object.ReferenceEquals (Code Inlined - Fastest method)

if foo=Nothing Then

Operators.ConditionalCompareObjectEqual(foo, Nothing, False)

Vb.Net carry this case like Obj1 = Obj2. It do´nt uses Obj.equals(obj2) ! Exception if Obj1 is nothing

This option uses a very complex code as there are a lot options depending all posible foo definitions.

try this:

Sub Main()
  Dim o As Object = 0
  Debug.Print(o Is Nothing)  'False
  Debug.Print(o = Nothing)   'True 
End Sub