C# Can I check if an IntPtr is null?

Question

I have an IntPtr field in my C# class.
It holds a reference to an object in a C++ library.

protected IntPtr ThingPtr;

At some stage I may or may not initialise it.

ThingPtr = FunctionInMyCplusplusLibrary();

I'm wondering if checking whether it is null makes sense in this context (to check whether it has been intialised or not)

if(ThingPtr == null)
{
    //Do stuff
}

Never. ever. presume ANYTHING to be initialized. So yes, it does make complete sense! — , Sep 19 '14 at 15:29
An `IntPtr` can never be `null`. Use `ThingPtr == IntPtr.Zero` instead. — D Stanley, Sep 19 '14 at 15:31
Not exactly a duplicate but this is an answer that you should read http://stackoverflow.com/questions/1456861/is-intptr-zero-equivalent-to-null — Steve, Sep 19 '14 at 15:31
Structs are value types and cannot be null while objects are reference types and can be null. — Sam, Sep 19 '14 at 15:32

score 63 · Accepted Answer · answered Sep 19 '14 at 15:30

63

IntPtr is a value type and cannot be null.

You want to check whether it has a value of (address) 0:

if (ThingPtr == IntPtr.Zero)

answered Sep 19 '14 at 15:30

SLaks

An alternative is default(IntPtr) which I suspect is equivalent to IntPtr.Zero. If you want to specify the default value for a parameter, IntPtr.Zero won't work, but you can specify default(IntPtr), for example void TestMethod ( IntPtr p = default(IntPtr) ) – Phil Jollans Jul 22 '21 at 15:19

score 4 · Answer 2 · answered Sep 19 '14 at 15:30

4

IntPtr is a struct it can never be null, your library may return the equivalent of null but I expect that would be zero.

answered Sep 19 '14 at 15:30

Jaycee

score 3 · Answer 3 · answered Sep 19 '14 at 15:30

3

You can use IntPtr.Zero for null, however it's not equivalent to C# null value.

answered Sep 19 '14 at 15:30

brz

3 Answers3