wiform实现单个应用程序，并可以激活

 

public class SingleApplication
    {
        private const int SW_RESTORE = 9;
        private static string sTitle;
        private static IntPtr windowHandle;

        /// <summary>
        /// Imports 
        /// </summary>
        [DllImport("user32.Dll")]
        private static extern int EnumWindows(EnumWinCallBack callBackFunc, int lParam);

        [DllImport("User32.Dll")]
        private static extern void GetWindowText(int hWnd, StringBuilder str, int nMaxCount);

        [DllImport("user32.dll", EntryPoint = "SetForegroundWindow")]
        private static extern bool SetForegroundWindow(IntPtr hWnd);

        [DllImport("user32.dll")]
        private static extern Boolean ShowWindow(IntPtr hWnd, Int32 nCmdShow);

        /// <summary>
        /// EnumWindowCallBack
        /// </summary>
        /// <param name="hwnd"></param>
        /// <param name="lParam"></param>
        /// <returns></returns>
        private static bool EnumWindowCallBack(int hwnd, int lParam)
        {
            windowHandle = (IntPtr) hwnd;

            StringBuilder sbuilder = new StringBuilder(256);
            GetWindowText((int) windowHandle, sbuilder, sbuilder.Capacity);
            string strTitle = sbuilder.ToString();

            if (strTitle == sTitle)
            {
                ShowWindow(windowHandle, SW_RESTORE);
                SetForegroundWindow(windowHandle);
                return false;
            }
            return true;
        } //EnumWindowCallBack

        /// <summary>
        /// Execute a form base application if another instance already running on
        /// the system activate previous one
        /// </summary>
        /// <param name="frmMain">main form</param>
        /// <returns>true if no previous instance is running</returns>
        public static bool Run(Form frmMain)
        {
            sTitle = frmMain.Text;

            if (EnumWindows(EnumWindowCallBack, 0) == 0)
            {
                return false;
            }
            Application.Run(frmMain);
            return true;
        }

        public static bool Run(string frmText)
        {
            sTitle = frmText;

            if (EnumWindows(EnumWindowCallBack, 0) == 0)
            {
                return false;
            }
            return true;
        }

        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public static bool Run()
        {
            Process pr = Process.GetCurrentProcess();
            string strProcessName = pr.ProcessName;
            if (Process.GetProcessesByName(strProcessName).Length > 1)
            {
                return false;
            }
            return true;
        }

        #region Nested type: EnumWinCallBack

        private delegate bool EnumWinCallBack(int hwnd, int lParam);

        #endregion
    }

 

调用方式：

if (SingleApplication.Run("Form1"))//Form1为应用程序入口窗体
    Application.Run(new Form1());

//或者
//if (SingleApplication.Run(new Form1().Text))//Form1为应用程序入口窗体
    //Application.Run(new Form1());

//或者
//SingleApplication.Run(new Form1())