マイクロソフトが実現した取得プロセスのメインウィンドウハンドルコード

public class MyProcess

{

    private bool haveMainWindow = false;

    private IntPtr mainWindowHandle = IntPtr.Zero;

    private int processId = 0;



    private delegate bool EnumThreadWindowsCallback(IntPtr hWnd, IntPtr lParam);



    public IntPtr GetMainWindowHandle(int processId)

    {

        if (!this.haveMainWindow)

        {

            this.mainWindowHandle = IntPtr.Zero;

            this.processId = processId;

            EnumThreadWindowsCallback callback = new EnumThreadWindowsCallback(this.EnumWindowsCallback);

            EnumWindows(callback, IntPtr.Zero);

            GC.KeepAlive(callback);



            this.haveMainWindow = true;

        }

        return this.mainWindowHandle;

    }



    private bool EnumWindowsCallback(IntPtr handle, IntPtr extraParameter)

    {

        int num;

        GetWindowThreadProcessId(new HandleRef(this, handle), out num);

        if ((num == this.processId) && this.IsMainWindow(handle))

        {

            this.mainWindowHandle = handle;

            return false;

        }

        return true;

    }



    private bool IsMainWindow(IntPtr handle)

    {

        return (!(GetWindow(new HandleRef(this, handle), 4) != IntPtr.Zero) && IsWindowVisible(new HandleRef(this, handle)));

    }



    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]

    public static extern bool EnumWindows(EnumThreadWindowsCallback callback, IntPtr extraData);



    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]

    public static extern int GetWindowThreadProcessId(HandleRef handle, out int processId);



    [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]

    public static extern IntPtr GetWindow(HandleRef hWnd, int uCmd);



    [DllImport("user32.dll", CharSet = CharSet.Auto)]

    public static extern bool IsWindowVisible(HandleRef hWnd);

}