C#只打开一个窗口(程序)

控制窗口打开一次   private void mybutton_add_Click(object sender, EventArgs e) 

{ 

    FormCollection form_is_running = Application.OpenForms; 

    if (form_is_running["Form_add"] != null) 

    { 

        (form_is_running["Form_add"] as Form).Focus(); 

    } 

    else 

    { 

        Form_add form_add = new Form_add(); 

        form_add.Show(); 

    } 

} 

控制程序只运行一次
Class  Form1:Form 

{ 

        public Mutex mymutex; 

//-------------------------------在构造函数中加入 

        public Form1()  

        { 

         mymutex = new Mutex(false, "SINGLE_INSTANCE_MUTEX"); 

         if (!mymutex.WaitOne(0, false))  

         { 

             mymutex.Close(); 

             mymutex = null; 

         } 

        } 

}  

//_-------------------------------Dispose方法中加入一行 

 

       protected override void Dispose(bool disposing) 

        { 

            if (disposing && (components != null)) 

            { 

                components.Dispose(); 

                mymutex.ReleaseMutex(); //---------此行 

            } 

            base.Dispose(disposing); 

        } 

 

//----------------------------------Main方法中，如果是不同类，请建立实例。  

   static class Program 

    { 

        /// <summary> 

        /// The main entry point for the application. 

        /// </summary> 

        ///  

        /// 

        [STAThread] 

        static void Main() 

        { 

            Application.EnableVisualStyles(); 

            Application.SetCompatibleTextRenderingDefault(false); 

            Form1 form1 = new Form1(); 

            if (form1.mymutex != null)  

            Application.Run(form1); 

        } 

    }