windows程序里新窗体不在任务栏显示，无标题拖动，键盘事件，始终显示在主窗体上面，单实例运行等

1. 不显示在任务栏,Alt+Tab也不显示

           protected override CreateParams CreateParams
           {
               get
               {
                   const int WS_EX_APPWINDOW = 0x40000;
                   const int WS_EX_TOOLWINDOW = 0x80;
                   CreateParams cp = base.CreateParams;
                   cp.ExStyle &= (~WS_EX_APPWINDOW);    // 不显示在TaskBar
                   cp.ExStyle |= WS_EX_TOOLWINDOW;      // 不显示在Alt-Tab
                   return cp;
               }
           }
   

2. 无标题拖动

           [DllImport("user32.dll")]
           public static extern bool ReleaseCapture();
           [DllImport("user32.dll")]
           public static extern bool SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);
           public const int SC_MOVE = 0xF010;
           public const int HTCAPTION = 0x0002;
           public const Int32 WM_SYSCOMMAND = 274;
           private void picMain_MouseDown(object sender, MouseEventArgs e)
           {
               ReleaseCapture();
               SendMessage(this.Handle, WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0);
           }
   

3. 键盘事件

           protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
           {
               int WM_KEYDOWN = 256;
               int WM_SYSKEYDOWN = 260;
               if (msg.Msg == WM_KEYDOWN | msg.Msg == WM_SYSKEYDOWN)
               {
                   switch (keyData)
                   {
                       case Keys.Escape:
                           this.WindowState = FormWindowState.Normal;
                           return false;
                       case Keys.Enter:
                           this.WindowState = FormWindowState.Maximized;
                           return false;
                       case Keys.Up:
                       case Keys.Left:
                           return false;
                       case Keys.Right:
                       case Keys.Down:
                           return false;
                   }
               }
               return base.ProcessCmdKey(ref msg, keyData);
           }
   

4. 新建Form始终显示在主窗体上面

           [DllImport("user32 ")]
           public static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);
   
               Form frm = new Form();
               SetParent(frm.Handle, this.Handle);
   

   检测是否有实例

               bool createNew;
               using (System.Threading.Mutex m = new System.Threading.Mutex(true, "Global\\" + Application.ProductName, out createNew))
               {
                   if (createNew)
                   {
   /// 执行创建工作
   }
    else
                   {
                       /// 激活现有实例
                   }
               }
   

5. 激活现有实例

           [DllImport("user32.dll")]
           public static extern bool IsIconic(IntPtr hWnd);
           //隐藏窗口，活动状态给令一个窗口
           private const int SW_HIDE = 0;
           //用原来的大小和位置显示一个窗口，同时令其进入活动状态
           private const int SW_SHOWNORMAL = 1;
           //最小化窗口，并将其激活
           private const int SW_SHOWMINIMIZED = 2;
           //最大化窗口，并将其激活
           private const int SW_SHOWMAXIMIZED = 3;
           //用最近的大小和位置显示一个窗口，同时不改变活动窗口
           private const int SW_SHOWNOACTIVATE = 4;
           //用原来的大小和位置显示一个窗口，同时令其进入活动状态
           private const int SW_RESTORE = 9;
           //根据默认 创建窗口时的样式 来显示
           private const int SW_SHOWDEFAULT = 10;
           [DllImport("User32.dll")]
           public static extern bool ShowWindowAsync(System.IntPtr hWnd, int cmdShow);
           [DllImport("User32.dll")]
           public static extern bool SetForegroundWindow(System.IntPtr hWnd);
   
           public static void RaiseOtherProcess()
           {
               Process proc = Process.GetCurrentProcess();
               Process.GetProcesses();
               foreach (Process otherProc in
                   Process.GetProcessesByName(Process.GetCurrentProcess().ProcessName))
               {
                   if (proc.Id != otherProc.Id)
                   {
                       IntPtr hWnd = otherProc.MainWindowHandle;
                       if (IsIconic(hWnd))
                       {
                           ShowWindowAsync(hWnd, SW_RESTORE);
                       }
                       SetForegroundWindow(hWnd);
                       break;
                   }
               }
           }