「C#」Singletonデスクトップアプリケーションのdemo

2014年6月26日

処理コード：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace SingletonDesktopAppDemo
{
    static class Program
    {
        #region Win32 API

        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr FindWindow(ref string lpClassName, ref string lpWindowName);

        private enum WindowShowStyle : uint
        {
            /// <summary>Hides the window and activates another window.</summary>
            /// <remarks>See SW_HIDE</remarks>
            Hide = 0,
            /// <summary>Activates and displays a window. If the window is minimized 
            /// or maximized, the system restores it to its original size and 
            /// position. An application should specify this flag when displaying 
            /// the window for the first time.</summary>
            /// <remarks>See SW_SHOWNORMAL</remarks>
            ShowNormal = 1,
            /// <summary>Activates the window and displays it as a minimized window.</summary>
            /// <remarks>See SW_SHOWMINIMIZED</remarks>
            ShowMinimized = 2,
            /// <summary>Activates the window and displays it as a maximized window.</summary>
            /// <remarks>See SW_SHOWMAXIMIZED</remarks>
            ShowMaximized = 3,
            /// <summary>Maximizes the specified window.</summary>
            /// <remarks>See SW_MAXIMIZE</remarks>
            Maximize = 3,
            /// <summary>Displays a window in its most recent size and position. 
            /// This value is similar to "ShowNormal", except the window is not 
            /// actived.</summary>
            /// <remarks>See SW_SHOWNOACTIVATE</remarks>
            ShowNormalNoActivate = 4,
            /// <summary>Activates the window and displays it in its current size 
            /// and position.</summary>
            /// <remarks>See SW_SHOW</remarks>
            Show = 5,
            /// <summary>Minimizes the specified window and activates the next 
            /// top-level window in the Z order.</summary>
            /// <remarks>See SW_MINIMIZE</remarks>
            Minimize = 6,
            /// <summary>Displays the window as a minimized window. This value is 
            /// similar to "ShowMinimized", except the window is not activated.</summary>
            /// <remarks>See SW_SHOWMINNOACTIVE</remarks>
            ShowMinNoActivate = 7,
            /// <summary>Displays the window in its current size and position. This 
            /// value is similar to "Show", except the window is not activated.</summary>
            /// <remarks>See SW_SHOWNA</remarks>
            ShowNoActivate = 8,
            /// <summary>Activates and displays the window. If the window is 
            /// minimized or maximized, the system restores it to its original size 
            /// and position. An application should specify this flag when restoring 
            /// a minimized window.</summary>
            /// <remarks>See SW_RESTORE</remarks>
            Restore = 9,
            /// <summary>Sets the show state based on the SW_ value specified in the 
            /// STARTUPINFO structure passed to the CreateProcess function by the 
            /// program that started the application.</summary>
            /// <remarks>See SW_SHOWDEFAULT</remarks>
            ShowDefault = 10,
            /// <summary>Windows 2000/XP: Minimizes a window, even if the thread 
            /// that owns the window is hung. This flag should only be used when 
            /// minimizing windows from a different thread.</summary>
            /// <remarks>See SW_FORCEMINIMIZE</remarks>
            ForceMinimized = 11
        }

        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
        [DllImport("User32")]
        private static extern int SetForegroundWindow(IntPtr hwnd);
        [DllImport("user32.dll")]
        private static extern bool ShowWindow(IntPtr hWnd, WindowShowStyle nCmdShow);

        #endregion

        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            // Open or create named mutex
            Mutex pMutex = new Mutex(false, Application.ProductName);

            // Get ownershiip of mutex
            if (!pMutex.WaitOne(0, false))
            {
                // Mutex owned by someone else

                // The window's caption(i.e. Form.Text) should be same with 
                // the window you want to open(e.g. main form's caption).
                string windowName = "MyApp";

                IntPtr hWnd = FindWindow(null, windowName);
                if (hWnd != IntPtr.Zero)
                {
                    ShowWindow(hWnd, WindowShowStyle.Restore);
                    SetForegroundWindow(hWnd);
                    // MessageBox.Show("App already running!" );
                }
                else
                {
                    MessageBox.Show("could not find window");
                }
            }
            else
            {
                Run();
                // release mutex when done...
                pMutex.ReleaseMutex();
                return;
            }
        }

        static void Run()
        {
            Form myApp = new Form();
            myApp.Text = "MyApp";
            // Here goes you Application.Run(...) etc.
            Application.EnableVisualStyles();
            Application.Run(myApp);
        }
    }
}