实现同时只允许运行一个程序实例

方法一:

/// <summary>
/// 从这里开始运行
/// </summary>
[STAThread]
static void Main()
{
    Process instance = RunningInstance();
    if (instance == null)
    {
        //没有实例在运行
        WeatherApp appInstance = new WeatherApp();
        appInstance.StartMainGui();
    }
    else
    {
        //已经有一个实例在运行
        HandleRunningInstance(instance);
    }
}
#region 确保只有一个实例
public static Process RunningInstance()
{
    Process current = Process.GetCurrentProcess();
    Process[] processes = Process.GetProcessesByName(current.ProcessName);
    //遍历与当前进程名称相同的进程列表
    foreach (Process process in processes)
    {
        //Ignore the current process
        if (process.Id != current.Id)
        {
            //Make sure that the process is running from the exe file.
            if (Assembly.GetExecutingAssembly().Location.Replace("/", "//") == current.MainModule.FileName)
            {
                //Return the other process instance.
                return process;
            }
        }
    }
    return null;
}
private static void HandleRunningInstance(Process instance)
{
    MessageBox.Show("该应用系统已经在运行！", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Information);
    ShowWindowAsync(instance.MainWindowHandle, 1); //调用api函数，正常显示窗口
    SetForegroundWindow(instance.MainWindowHandle); //将窗口放置最前端。
}
[DllImport("User32.dll")]
private static extern bool ShowWindowAsync(System.IntPtr hWnd, int cmdShow);
[DllImport("User32.dll")]
private static extern bool SetForegroundWindow(System.IntPtr hWnd);
#endregion
 

方法二:

[STAThread]
static void Main(string[] args)
{
    bool isFirst;

    System.Threading.Mutex mutex = new System.Threading.Mutex(true, "WindowAppTest", out isFirst);
    //这里的myApp是程序的标识,建议换成你的程序的物理路径,这样的话如果在一个操作系统中这个标志不会和其它程序冲突
    if (!isFirst)
    {
        MessageBox.Show("Exist");
        Environment.Exit(1);//实例已经存在,退出程序
    }
    else
    {
        Application.Run(new Form1());
    }
}