学步园

添加引用

using System.Reflection;
using System.Runtime.InteropServices;
using System.Diagnostics;

调用DLL文件

[DllImport("User32.dll")]
private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
[DllImport("User32.dll")]
private static extern bool SetForegroundWindow(IntPtr hWnd);
private const int WS_SHOWNORMAL = 1;

添加如下两个函数

public static Process RunningInstance()
{
    Process current = Process.GetCurrentProcess();
    Process[] processes = Process.GetProcessesByName(current.ProcessName);

    //Loop   through   the   running   processes   in   with   the   same   name
    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;
            }
        }
    }

    //No   other   instance   was   found,   return   null.
    return null;
}
public static void HandleRunningInstance(Process instance)
{
    //Make   sure   the   window   is   not   minimized   or   maximized
    ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL);

    //Set   the   real   intance   to   foreground   window
    SetForegroundWindow(instance.MainWindowHandle);
}

在MAIN中添加如下代码

public static void Main()
{
    Process instance = RunningInstance();
    if (instance == null)
    {
        Application.Run(new Form1());
    }
    else
    {
        HandleRunningInstance(instance);
    }
}