如何防止重复打开窗体，如果重复打开则显示当前点击的窗体

Question

    代码已经做到了，防止重复打开，但是我再重复点击的时候，该窗体不能作为焦点还是最小化在下面    private void add_sell_Click(object sender, EventArgs e)
        {            if (add_chuku.sign == false)
            {
                add_chuku asss = new add_chuku();
                asss.MdiParent = this;
                add_chuku.sign = true;
                asss.ShowDialog();
                
            }
            else
            {
               return;
            }
        }

Answer 1

正好我这篇适合你看
http://blog.csdn.net/wuyazhe/archive/2010/06/24/5690850.aspx

Answer 2

在“Program.cs”里加入如下代码：
        [DllImport("user32.dll ")]
        public static extern void SetForegroundWindow(IntPtr hwnd);
        [DllImport("user32.dll ")]
        public static extern IntPtr GetForegroundWindow();        [DllImport("user32.dll ")]
        public static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
        public static void ActiveiseLoginWindow(string name)
        {
            Process[] proc = Process.GetProcessesByName(name);            foreach (Process p in proc)
            {
                SetForegroundWindow(p.MainWindowHandle);
                ShowWindow(p.MainWindowHandle, 3);
            }        }      [STAThread]
        static void Main()
        {
            bool canCreateNew;
            Mutex mutex = new Mutex(true, "工程名", out canCreateNew);
            if (!canCreateNew)
            {
                //throw new Exception("Can create two or more server!");
                ActiveiseLoginWindow("工程名");                return;
            }            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
            mutex.ReleaseMutex();
        }

Answer 3

  
  private CustomerManagement.CustomerManger customanger;
        private void 客户信息ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (customanger == null || customanger.IsDisposed)
            {
                customanger = new AchievementManger.CustomerManagement.CustomerManger();
                customanger.MdiParent = this;
                customanger.Show();
            }
            else { customanger.Activate(); }
        }

Answer 4

add_chuku.sign == false  //这个是变量用来判断什么呀,判断窗体是否打开???看哪个代码好像没有判断窗体是否有打开的呀..页首声明add_chuku asss 变量  if (add_chuku.sign == false)
  {
  asss = new add_chuku();
  asss.MdiParent = this;
  add_chuku.sign = true;
  asss.ShowDialog();
    
  }
  else
  {
  asss.Focus();
  return;
  }

Answer 5

add_chuku.sign == false
这个就是判断窗体是否打开的。