[1.0/1.1] Use mutex to find the multiple instance

[eranga262154]

Hi all,

I have write a service to automate a server application. To start the application I need some IPs which are stored in a database. I read the database and get required IPs on my service and run the server.

Up to now everything is ok.

Now I want to check that there is multiple instance are available. Because I can start only one server at a time. To do this I try to use MUTEX, as in C++(my server is written on C++). Can you guys give me a help. I don't know that higher concepts to handle in C#.

Thanks a lot.

[daimous]

try this...

       [STAThread]
        static void Main()
        {
            string MutexName = "MutexNameHere";
            bool grantedOwnership;
            System.Threading.Mutex singleIntanceMutex = new System.Threading.Mutex(true, MutexName, out grantedOwnership);
            try
            {
                if (grantedOwnership)
                {
                    Application.EnableVisualStyles();
                    Application.SetCompatibleTextRenderingDefault(false);
                    Application.Run(new frmIndex());
                }
                else
                {
                    MessageBox.Show("Another Instance of this application is already running.", "BCMD", MessageBoxButtons.OK, MessageBoxIcon.Information);

                }
            }
            finally
            {
                singleIntanceMutex.Close();
            }


        }

[Paul M]

Heres another way

static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            
            int count = CheckForRunningInstances();

            if (count <= 1)
            {
                Application.Run(new Form1());
            }
            else
            {
                System.Windows.Forms.MessageBox.Show("Another instance of this program is already running.  Two instances cannot run at the same time", "Already running", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                Application.Exit();
            }

        }
        private static int CheckForRunningInstances()
        {

            string[] parts = System.Reflection.Assembly.GetExecutingAssembly().Location.Split("\\".ToCharArray());
            string appName = parts[parts.Length - 1];

            string query = "select name from CIM_Process where name = '" + appName + "'";

            System.Management.ManagementObjectSearcher searcher = new System.Management.ManagementObjectSearcher(query);

            int hInstCount = 0;

            foreach (System.Management.ManagementObject item in searcher.Get())
            {
                hInstCount++;
                if (hInstCount > 1) break;
            }
            return hInstCount;
        }

[Kasracer]

My codebank submission submitted in early 2006: http://www.vbforums.com/showthread.php?t=397006

Heres another way

That's horribly inefficient especially compared to the simplicity of using a mutex.

[Paul M]

mutex is just easier to use, this one gives you a lot more options

[Kasracer]

mutex is just easier to use, this one gives you a lot more options

I fail to see how it gives you more options. You're just iterating through assemblies and using more memory and cpu than necessary. If you can come up with any advantages I'd love to hear them though. I love learning new techniques.

As for mutex; a mutex is the propery way to accomplish single instances. Most single instance C++ applications also use this technique.

[Paul M]

        private static int GetNumberOfRunningInstances()
        {
            int runcount = 0;

            string[] parts = System.Reflection.Assembly.GetExecutingAssembly().Location.Split("\\".ToCharArray());
            string appName = parts[parts.Length - 1];

            string query = "select name from CIM_Process where name = '" + appName + "'";

            System.Management.ManagementObjectSearcher searcher = new System.Management.ManagementObjectSearcher(query);

            foreach (System.Management.ManagementObject item in searcher.Get())
            {
                runcount++;
            }
            return runcount;
        }

That was my original code for a project i had to make that had to check the number of running instances. But the assembly class also allows the developer to further explore the assembly if required. I only edited and posted the code for fun and just to show another way. But for something as simple as to only allow one instance mutex would best serve the developer as it is basically its primary job.

[Kasracer]

The assembly you're looking for should be your own... so why would you need to explore it further?

[axion_sa]

        private static int GetNumberOfRunningInstances()
        {
            int runcount = 0;

            string[] parts = System.Reflection.Assembly.GetExecutingAssembly().Location.Split("\\".ToCharArray());
            string appName = parts[parts.Length - 1];

            string query = "select name from CIM_Process where name = '" + appName + "'";

            System.Management.ManagementObjectSearcher searcher = new System.Management.ManagementObjectSearcher(query);

            foreach (System.Management.ManagementObject item in searcher.Get())
            {
                runcount++;
            }
            return runcount;
        }

That was my original code for a project i had to make that had to check the number of running instances. But the assembly class also allows the developer to further explore the assembly if required. I only edited and posted the code for fun and just to show another way. But for something as simple as to only allow one instance mutex would best serve the developer as it is basically its primary job.

Won't work if your application is hosted in a secondary AppDomain

[eranga262154]

Thanks pal for your code. But I'm confusing with that Forms and Service I have work on. I'll check it and back, if I stuck.

[eranga262154]

Heres another way

static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            
            int count = CheckForRunningInstances();

            if (count <= 1)
            {
                Application.Run(new Form1());
            }
            else
            {
                System.Windows.Forms.MessageBox.Show("Another instance of this program is already running.  Two instances cannot run at the same time", "Already running", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                Application.Exit();
            }

        }
        private static int CheckForRunningInstances()
        {

            string[] parts = System.Reflection.Assembly.GetExecutingAssembly().Location.Split("\\".ToCharArray());
            string appName = parts[parts.Length - 1];

            string query = "select name from CIM_Process where name = '" + appName + "'";

            System.Management.ManagementObjectSearcher searcher = new System.Management.ManagementObjectSearcher(query);

            int hInstCount = 0;

            foreach (System.Management.ManagementObject item in searcher.Get())
            {
                hInstCount++;
                if (hInstCount > 1) break;
            }
            return hInstCount;
        }

Thanks, but I got an error on "Application" that namespace is not found. I couldn't find the definition either. What should I do.

[eranga262154]

Ok, here is the best explanation I have on this question.

I have a server application written using C++. Now I try to automate the server to start it automatically. So I write a .Net service to do that.

It's fine, my service is working fine.

But there is one issue. Actually my server can't run multiple server using the same IP. So I want to find is there any server running on specific IP.

So, I used Mutex.

Here what I have done. First get the each server IP from a data base and on each one test there is any instance going on.

		private bool HasMultipleInstance(string IP)
		{
			/*
			 * No need to acquire or release the Mutex in .Net
			 * */
			IPMutex = new Mutex( true, IP + "_mutex_" );
			//IPMutex.WaitOne();	

			if( IPMutex != null )
			{
				EventLog.WriteEntry( "MyService", "Multiple Instances on " + IP );
				//IPMutex.ReleaseMutex(); 
				return false;
			}
			else
				return true;
		}

What is your guys comment on this. Is that ok? Actually it write an entry to the event log, when a multiple instance is found..

Thanks a lot