How to ensure only one instance of application should run in C#

It can be achieved by using mutex.

A Mutex is a mutually exclusive flag. It acts as a gate keeper to a section of code allowing one thread in and blocking access to all others. This ensures that the code being controlled will only be hit by a single thread at a time. Just be sure to release the mutex when you are done.

Below is the sample program:

In this program I am creating a mutex which is taking care of single instance of application should run.

There are three parameter  

1.     initallyOwned:- Boolean value(true)

2.    Name - string

3.    Creatednew – out parameter Boolean value

using System;

using System.Collections.Generic;

using System.Linq;

using System.Windows.Forms;

using System.Threading;

namespace Questions

    {

        static class Program

        {

            /// <summary>

            /// The main entry point for the application.

            /// </summary>

            [STAThread]

            static void Main()

            {

                bool mutexCreated = false;

                System.Threading.Mutex mutex = new System.Threading.Mutex( true, @"QuestionProgram", out mutexCreated );

                               

                if (!mutexCreated)

                {

                    MessageBox.Show("QuestionProgram is already running.");

                }

                else

                {

                    // The usual stuff with Application.Run()

                    Application.EnableVisualStyles();

                    Application.SetCompatibleTextRenderingDefault(false);

                    Application.Run(new Form1());

                    mutex.Close();

                }

            }

           

        }

        

    }