'Is' pattern in pointers

[kyoyama-kazusa]

Hello.

C# allows is pattern on pointers, but I can't figure the differences out between pointer == null and pointer is null. I wonder that what real differences between those two kinds of the code style of comparison. Or in other words, why I should use pointer is null instead of pointer == null or vice versa?

Test code:

using System;

unsafe
{
    int* p = null;
    delegate*<void> q = null;

    if (p == null) Console.WriteLine(1);
    if (p is null) Console.WriteLine(1);

    if (p != null) Console.WriteLine(1);
    if (p is not null) Console.WriteLine(1);

    if (q == null) Console.WriteLine(1);
    if (q is null) Console.WriteLine(1);

    if (q != null) Console.WriteLine(1);
    if (q is not null) Console.WriteLine(1);
}

See this link (SharpLab)

Thanks.

[huoyaoyuan]

I believe the real reason is syntax matrix completeness, because we don't have a reason to ban it.
Allowing pointers to be handled by pattern matching is useful for nested cases like is { PointerProp: not null }.

[kyoyama-kazusa]

Oh, that sounds reasonable! Thank you!