Make your app opens just ones when it already open

Make your c# and vb.net app opens just ones when it already open
 This is a simple idea to Cleary,  meaning that the user open the program , he can't open another one in the same time,  the idea depends to md5 hash count of the application,

Then bring all processes running in the machine, and count their own md5 hash , and made the comparison between process hash and  our program hash , and in the case of a match, the program is to make sure first that the process is not its own, if it  not , this means that the program is already open,and it will close it itself 

Let's get started...

If you are C# Developer
Ad this fuction to your project 

Copy all and past to your project 

string mdHASH(string prosfile) { using (var md5 = MD5.Create()) { try { return BitConverter.ToString(md5.ComputeHash(File.ReadAllBytes(prosfile))).Replace("-", ""); } catch { return null; } } }

Then add this code to the form load event

string myHash = mdHASH(Application.ExecutablePath); foreach (Process Pr in Process.GetProcesses()) { try { string prchash = mdHASH(Pr.MainModule.FileName); if (myHash == prchash) { if (!(Pr.Id == Process.GetCurrentProcess().Id)) Process.GetCurrentProcess().Kill(); } } catch { } }

The project needs to
using System.Security.Cryptography;
using System.IO;
using System.Diagnostics;

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Or If your vb.net developer its the same
Steps but with vb.net coding language

 Call those library 

Imqport those library :
Imports System.IO
Imports System.Security.Cryptography

 Add this function :

Function mdHASH(prosfile As String) As String Using md5__1 = MD5.Create() Try Return BitConverter.ToString(md5__1.ComputeHash(File.ReadAllBytes(prosfile))).Replace("-", "") Catch Return Nothing End Try End Using End Function

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Then this code in the form load event

 

Dim myHash As String = mdHASH(Application.ExecutablePath) For Each Pr As Process In Process.GetProcesses() Try Dim prchash As String = mdHASH(Pr.MainModule.FileName) If myHash = prchash Then If Not (Pr.Id = Process.GetCurrentProcess().Id) Then Process.GetCurrentProcess().Kill() End If End If Catch End Try Next

Download simple project

This it , you done here , hope you get what you need
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