Is IntPtr.Zero equivalent to null?

Question

I am trying to setup ReadFile to run asynchronously and according to MSDN, I need to set lpNumberOfBytesRead to null:

Answer 1

Be aware that there is a bug (feature??) in C# >= 2.0, where

if (IntPtr.Zero == null)
{
    // Won't enter here
}

will compile correctly, but it won't ever enter in the if.

I opened an issue on the github of roslyn and they replied that they won't fix it because there are projects that are built with warnings-as-errors. Still there is a partial fix for this: there is a strict compilation mode that generates this warning:

<Features>strict</Features>

Answer 2

You cannot assign null to a value-type. A reference-type can be null, as in, not referring to an object instance, but a value-type always has a value.

IntPtr.Zero is just a constant value that represents a null pointer.

Answer 3

For P/Invoke purposes like you've listed, you should use IntPtr.Zero in place of NULL. Note that this is not equivalent to the C# null keyword, however.