Getting the size of the array pointed to by IntPtr

Question

I have a native C++ function that I call from a C# project using pinvoke.

extern \"C\" _declspec(dllexport) void GetCmdKeyword( wchar_t** cmdKeyword, uint  pCmd         


        

Answer 1

You cannot infer the length from the pointer. The information must be passed as a separate value alongside the pointer to the array.

I wonder why you use raw IntPtr rather than C# arrays. I think the answer you accepted to your earlier question has the code that you need: Pinvoking a native function with array arguments.

---

OK, looking at the edit to the question, the actual scenario is a little different. The function returns a pointer to a null-terminated array of wide characters. Your pinvoke should be:

[DllImport(...)]
static extern void GetCmdKeyword(out IntPtr cmdKeyword, uint pCmdNum);

Call it like this:

IntPtr ptr;
GetCmdKeyword(ptr, cmdNum);
string cmdKeyword = Marshal.PtrToStringUni(ptr);