Winform只允许运行一个实例

修改Program.cs，其中Scanning改成具体的项目名称

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

namespace Scanning
{
    internal static class Program
    {
        [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 SwShownomal = 1;
        private static void HandleRunningInstance(Process instance)
        {
            ShowWindowAsync(instance.MainWindowHandle, SwShownomal);//显示            
            SetForegroundWindow(instance.MainWindowHandle);//当到最前端
        }

        private static Process RunningInstance()
        {
            using (var currentProcess = Process.GetCurrentProcess())
            {
                var processes = Process.GetProcessesByName(currentProcess.ProcessName);
                foreach (var process in processes)
                {
                    if (process.Id == currentProcess.Id) continue;
                    if (Assembly.GetExecutingAssembly().Location.Replace("/", "\\") == currentProcess.MainModule?.FileName)
                    {
                        return process;
                    }
                }
            }

            return null;
        }

        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        private static void Main()
        {
            var process = RunningInstance();
            if (process == null)
            {
                Application.EnableVisualStyles();
                Application.SetCompatibleTextRenderingDefault(false);

                Application.Run(new Scanning());

            }
            else
            {
                HandleRunningInstance(process);
                Environment.Exit(1);
            }
        }
    }
}