Question

I want to use WinApi function ComboBox_SetCurSel in my C# application.

For this purpose I insert following statement:

[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr ComboBox_SetCurSel(IntPtr hWnd, int index);

When I run the program, I get the error

EntryPointNotFoundException ComboBox_SetCurSel user32.dll
  Message=Can't find entry point "ComboBox_SetCurSel" in DLL "user32.dll".

I suppose that this error is caused by ComboBox_SetCurSel being located not in user32.dll, but in some other DLL.

If this is correct, to fix this error I need to change DllImport declaration.

Question: In what DLL is ComboBox_SetCurSel located?

Answer 1

That’s not actually a function. It’s a macro, from WindowsX.h:

#define ComboBox_SetCurSel(hwndCtl, index)          ((int)(DWORD)SNDMSG((hwndCtl), CB_SETCURSEL, (WPARAM)(int)(index), 0L))

Where SNDMSG is SendMessage. In other words you should do:

[DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam);

SendMessage(hWnd, 0x14E, (Int32)index, 0);