Using overloaded VB.NET Not operator from C#

Question

I have a VB class which overloads the Not operator; this doesn't seem to be usable from C# applications.

Public Shared Operator Not(item As MyClass) As Boolean
    Return False
End Operator

I can use this in VB.NET:

If Not MyClassInstance Then
    ' Do something
End If

I am trying to us this in a C# application but it won't build.

if (!MyClassInstance) 
{ 
     // do something
}

I get the error

Operator '!' cannot be applied to operand of type 'MyClass'

Can anyone tell me what I am missing?

try writing the class name with parameter braces because you have to call that function that's returning a boolean value. i.e if(!MyClassInstance()) { // do something } — sohaiby
– sohaiby, Commented Dec 12, 2014 at 18:59

Ry- · Accepted Answer · 2018-02-07 18:24:30Z

15

The Not operator in VB.NET is a bitwise operator, it produces the one's complement of its operand. It doesn't have the equivalent of C#'s ! operator, a logical operator. You must use the equivalent bitwise operator in C# to use your VB.NET operator overload:

if(~MyClassInstance) 
{ 
     // do something
}

You can write a function in VB.NET that will map to the C# logical operator. That needs to look like this:

<System.Runtime.CompilerServices.SpecialName> _
Public Shared Function op_LogicalNot(item As MyClass) As Boolean
    Return False
End Function

edited Feb 7, 2018 at 18:24

Ry-♦

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answered Dec 12, 2014 at 19:04

Hans Passant

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2 Comments

english fool Over a year ago

Thank you for the explaination, unfortunately if I use the op_LogicalNot I am not allowed to also use the VB Not operator, so I can have it strange in VB or strange in C#. I will just stick to using the bitwise operator in C#.

english fool Over a year ago

Fascinating, Visual studio complains that a method with the same name is declared twice, but it does build and run. Cheers.

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