Question

I’m trying to use a class named CFindWnd. Unfortunately it’s written in C and I don’t have a clue how to translate it into C# (or any other language that I know). As it is not a very large class, I am hoping to find a helpful soul that is willing to translate it for me.

////////////////////////////////////////////////////////////////
// MSDN Magazine -- August 2003
// If this code works, it was written by Paul DiLascia.
// If not, I don't know who wrote it.
// Compiles with Visual Studio .NET on Windows XP. Tab size=3.
//
// ---
// This class encapsulates the process of finding a window with a given class name
// as a descendant of a given window. To use it, instantiate like so:
//
//        CFindWnd fw(hwndParent,classname);
//
// fw.m_hWnd will be the HWND of the desired window, if found.
//
class CFindWnd {
private:
    //////////////////
    // This private function is used with EnumChildWindows to find the child
    // with a given class name. Returns FALSE if found (to stop enumerating).
    //
    static BOOL CALLBACK FindChildClassHwnd(HWND hwndParent, LPARAM lParam) {
        CFindWnd *pfw = (CFindWnd*)lParam;
        HWND hwnd = FindWindowEx(hwndParent, NULL, pfw->m_classname, NULL);
        if (hwnd) {
            pfw->m_hWnd = hwnd;    // found: save it

            return FALSE;            // stop enumerating

        }
        EnumChildWindows(hwndParent, FindChildClassHwnd, lParam); // recurse

        return TRUE;                // keep looking
    }

public:
    LPCSTR m_classname;            // class name to look for

    HWND m_hWnd;                    // HWND if found

    // ctor does the work--just instantiate and go

    CFindWnd(HWND hwndParent, LPCSTR classname)
        : m_hWnd(NULL), m_classname(classname)
    {
        FindChildClassHwnd(hwndParent, (LPARAM)this);
    }
};

EDIT:
I have come up with the following. But I have still trouble converting from object to IntPtr and vice versa.

class CFindWnd
{
    [DllImport("user32.dll", SetLastError = true)]
    public static extern IntPtr FindWindowEx(IntPtr parentHandle, IntPtr childAfter, string className, IntPtr windowTitle);

    public delegate bool Win32Callback(IntPtr hwnd, IntPtr lParam);
    [DllImport("user32.Dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool EnumChildWindows(IntPtr parentHandle, Win32Callback callback, IntPtr lParam);


    private static bool FindChildClassHwnd(IntPtr hwndParent, IntPtr lParam)
    {
        CFindWnd pfw = lParam as CFindWnd; //??? Error: can not be converted
        IntPtr hwnd = FindWindowEx(hwndParent, IntPtr.Zero, pfw.m_classname, IntPtr.Zero);
        if (!hwnd.Equals(IntPtr.Zero)) //??? not sure if that is correct
        {
            pfw.m_hWnd = hwnd;    // found: save it
            return false;            // stop enumerating
        }
        EnumChildWindows(hwndParent, FindChildClassHwnd, lParam); // recurse
        return true;                // keep looking
    }


    public string m_classname;            // class name to look for
    public IntPtr m_hWnd;                    // HWND if found


    // ctor does the work--just instantiate and go
    public CFindWnd(IntPtr hwndParent, string classname)
    {
        m_hWnd = IntPtr.Zero;
        m_classname = classname;
        FindChildClassHwnd(hwndParent, this); //??? conversion error
    }
}

Answer 1

I have solved it. The solution is not quite a direct translation, because the original seems a bit too roundabout.
Usage: Call the static method handle = CFindWnd.FindHandle(parentHandle, classname) to get the handle of a window that is a descendant of parentHandle and has the name classname.
Example: Assuming you have a webbrowser control and want to manipulate the underlying Internet Explorer_Server directly, you can use CFindWnd.FindHandle(webbrowser.Handle, “Internet Explorer_Server”) to get it’s handle.

class CFindWnd
{
    [DllImport("user32.dll", SetLastError = true)]
    public static extern IntPtr FindWindowEx(IntPtr parentHandle, IntPtr childAfter, string className, IntPtr windowTitle);

    public delegate bool Win32Callback(IntPtr hwnd, IntPtr lParam);
    [DllImport("user32.Dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool EnumChildWindows(IntPtr parentHandle, Win32Callback callback, IntPtr lParam);


    static private bool FindChildClassHwnd(IntPtr parentHandle, IntPtr lParam)
    {
        IntPtr hwnd = FindWindowEx(parentHandle, IntPtr.Zero, _classname, IntPtr.Zero);
        if (!hwnd.Equals(IntPtr.Zero))
        {
            _handle = hwnd;           // found: save it
            return false;            // stop enumerating
        }
        EnumChildWindows(parentHandle, FindChildClassHwnd, lParam); // recurse
        return true;                 // keep looking
    }

    static private string _classname;              // class name to look for
    static private IntPtr _handle;                 // HWND if found

    static public IntPtr FindHandle(IntPtr parentHandle, string classname)
    {
        _handle = IntPtr.Zero;
        _classname = classname;
        FindChildClassHwnd(parentHandle, IntPtr.Zero);
        return _handle;
    }
}