Reference to an unresolved external symbol

[Injeckt via Digitalmars-d-learn]

Hi guys, I have an issue when I compile program with using 
windows api, I got this message:
"reference to an unresolved external symbol _MessageBoxW@16". I 
just created simple hello world using winapi and MessageBox.

    import core.runtime;
    import std.stdio;
    import std.string;
    import core.sys.windows.windows;
    extern(Windows)
    int WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 
LPSTR cmdLine, int nCmdShow) {
        int result;

        try {
            Runtime.initialize();
            result = myWinMain(hInstance, hPrevInstance, cmdLine, 
nCmdShow);
            Runtime.terminate();
        } catch (Throwable e) {
            result = 0;
        }

        return result;
    }

    int myWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 
LPSTR cmdLine, int nCmdShow) {
        MessageBox(null, "Hello", "D!", MB_OK);

        return 0;
    }