C# WPF，通过自定义协议，向其它进程发送参数

        /*
         * https://msdn.microsoft.com/zh-cn/library/843s5s5x%28v=vs.100%29.aspx
         * 输出本地计算机上每个窗口的句柄值
         * 使用 EnumWindows 函数来逐步浏览窗口列表，并使用一个托管回调函数（名为 WNDENUMPROC）来输出窗口句柄的值。
         */
        public delegate bool WNDENUMPROC(IntPtr hwnd, uint lParam);
        [DllImport("user32.dll", EntryPoint = "EnumWindows", SetLastError = true)]
        public static extern bool EnumWindows(WNDENUMPROC lpEnumFunc, uint lParam);

        /// <devdoc>http://msdn.microsoft.com/en-us/library/windows/desktop/ms633528(v=vs.85).aspx</devdoc>
        [DllImport("user32", CharSet = CharSet.Auto, ExactSpelling = true)]
        internal static extern bool IsWindow([In] [Optional] IntPtr hWnd);

        /*Retrieves a handle to the specified window‘s parent or owner.*/
　　　　 [DllImport("user32.dll", EntryPoint = "GetParent", SetLastError = true)]
        public static extern IntPtr GetParent(IntPtr hWnd);
        [DllImport("user32.dll", EntryPoint = "GetWindowThreadProcessId")]
        public static extern uint GetWindowThreadProcessId(IntPtr hWnd, ref uint lpdwProcessId);
        [DllImport("kernel32.dll", EntryPoint = "SetLastError")]
        public static extern void SetLastError(uint dwErrCode);

        private static Hashtable processWnd = new Hashtable();

        private static bool EnumWindowsProc(IntPtr hwnd, uint lParam)
        {
            uint uiPid = 0;

            if (GetParent(hwnd) == IntPtr.Zero)
            {
                GetWindowThreadProcessId(hwnd, ref uiPid);
                if (uiPid == lParam)    // 找到进程对应的主窗口句柄
                {
                    processWnd.Add(uiPid, hwnd);   // 把句柄缓存起来
                    SetLastError(0);    // 设置无错误
                    return false;   // 返回 false 以终止枚举窗口
                }
            }

            return true;
        }

        public static IntPtr GetCurrentWindowHandle(uint proid)
        {
            IntPtr ptrWnd = IntPtr.Zero;
            uint uiPid = proid;
            object objWnd = processWnd[uiPid];

            if (objWnd != null)
            {
                ptrWnd = (IntPtr)objWnd;
                if (ptrWnd != IntPtr.Zero && IsWindow(ptrWnd))  // 从缓存中获取句柄
                {
                    return ptrWnd;
                }
                else
                {
                    ptrWnd = IntPtr.Zero;
                }
            }

            bool bResult = EnumWindows(EnumWindowsProc, uiPid);
            // 枚举窗口返回 false 并且没有错误号时表明获取成功
            if (!bResult && Marshal.GetLastWin32Error() == 0)
            {
                objWnd = processWnd[uiPid];
                if (objWnd != null)
                {
                    ptrWnd = (IntPtr)objWnd;
                }
            }
            return ptrWnd;
        }

    [StructLayout(LayoutKind.Sequential)]
    public struct CopyDataStruct
    {
        public IntPtr dwData;
        public int cbData;//字符串长度
        [MarshalAs(UnmanagedType.LPStr)]
        public string lpData;//字符串
    }

        [DllImport("user32.dll")]
        public static extern void SendMessage(IntPtr hWnd, int msg, int wParam, ref CopyDataStruct lParam);

    public static class Constants
    {
        public const int WM_COPYDATA = 0x004A;
    }

        public static void SendMessage(Process process, string msg)
        {
            IntPtr hwnd = UnsafeNativeMethods.GetCurrentWindowHandle((uint)process.Id);
            CopyDataStruct d = new CopyDataStruct();
            d.dwData = IntPtr.Zero;
            d.lpData = msg;
            d.cbData = System.Text.Encoding.Default.GetBytes(msg).Length + 1;
            UnsafeNativeMethods.SendMessage(hwnd, Constants.WM_COPYDATA, 0, ref d);
        }

Loaded += MainWindow_Loaded;

        void MainWindow_Loaded(object sender, RoutedEventArgs e)
        {
            (PresentationSource.FromVisual(this) as HwndSource).AddHook(new HwndSourceHook(WndProc));
        }

    [StructLayout(LayoutKind.Sequential)]
    public struct CopyDataStruct
    {
        public IntPtr dwData;
        public int cbData;//字符串长度
        [MarshalAs(UnmanagedType.LPStr)]
        public string lpData;//字符串
    }

        IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            if (msg == Constants.WM_COPYDATA)
            {
                var cds = (CopyDataStruct)Marshal.PtrToStructure(lParam, typeof(CopyDataStruct));
                var cmd = cds.lpData;
                if (oid.IsNotEmpty())
                {
                   ...
                }
            }
            return hwnd;
        }