Re: System.Web.UI.Page, get page object from URL - C# Discussion Boards

9-Oct-07 3:26

Hi
I have an application and I want to keep only one instance running, so I use Mutex class. All works fine until I want to restart that application immediately. It looks that Mutex is not released synchronously with ReleaseMutex() call , but a little while later. My app code looks like :

static void Main()
{
Acquire Mutex

Run main form

Release Mutex

Restart same application using Process.Start(...);
}

When restarting application immediately, Mutex is still owned by old instance, which could not happen id all was synchronized probably...

Question:

How can I wait for the Mutex to be released for sure?
(maybe Thread.Sleep(1000) for a second after Releas call...) ?

thanx for answer

zilo

led mike9-Oct-07 5:34

9-Oct-07 5:34

I was not able to reproduce your problem. Perhaps you have more than one count on the Mutex?

Stevo Z9-Oct-07 6:05

9-Oct-07 6:05

I have only one mutex. I've temporary "solved" the problem by sleeping 1000 mls before (re)starting same process (to let Mutex time to Releas WTF | :WTF:

)

led mike9-Oct-07 6:13

9-Oct-07 6:13

Zilo(svk) wrote:
I have only one mutex.

Yes I know but you may have a count on it greater than ONE.

Zilo(svk) wrote:
I've temporary "solved" the problem by sleeping 1000 mls before (re)starting same process

I did not need to sleep. I suspect you have a bug in your code.

Stevo Z9-Oct-07 7:06

9-Oct-07 7:06

I have a wrapper class for Mutex described in here

I create one Mutex instance per one application instance, releasing that instance when application finished (before restarting).

logically, i should have a bug somewhere, but where Smile | :)

zilo

led mike9-Oct-07 7:20

9-Oct-07 7:20

Zilo(svk) wrote:
I create one Mutex instance per one application instance, releasing that instance when application finished (before restarting).

Yes, exactly what I tested, and I have no wrapper class because I don't need one to do that.

class MutexTest
{
	private Mutex _mut = new Mutex(false, "MutexTest");
	public void Run()
	{
		_mut.WaitOne();
		Console.WriteLine("MutexTest has mutex... going to sleep...");
		Thread.Sleep(10000);
		Console.WriteLine("MutexTest releasing");
		_mut.ReleaseMutex();
	}
	public bool IsLocked()
	{
		return _mut.WaitOne(0, false);
	}
}
class Program
{

	static int Main(string[] args)
	{
		MutexTest mt = new MutexTest();
		if (!mt.IsLocked())
			Console.WriteLine("Second Instance... exiting");
		else
		{
			mt.Run();
			System.Diagnostics.Process.Start("ConsoleRnd.exe");
			Console.WriteLine("Complete....");
		}

		return 0;
	}

Stevo Z9-Oct-07 22:47

9-Oct-07 22:47

Try this one:

<br />
<br />
public class SingleProgramInstance : IDisposable<br />
{<br />
       //private members <br />
        private Mutex __mutex;<br />
        private bool __firstInstance = false;<br />
        private string __uniqueName = String.Empty;<br />
       <br />
        private Mutex Mutex<br />
        {<br />
            get { return __mutex; }<br />
            private set { __mutex = value; }<br />
        }<br />
<br />
        public string UniqueName<br />
        {<br />
            get { return __uniqueName; }<br />
            private set { __uniqueName = value; }<br />
        }<br />
 <br />
        public SingleProgramInstance()<br />
            : this(String.Empty)<br />
        {      }<br />
        <br />
        public SingleProgramInstance(string identifier)<br />
        {<br />
            //Initialize a named mutex and attempt to<br />
            // get ownership immediately.<br />
            //Use an addtional identifier to lower<br />
            // our chances of another process creating<br />
            // a mutex with the same name.<br />
<br />
            this.UniqueName =  Assembly.GetExecutingAssembly().GetName().Name + identifier;<br />
<br />
            this.Mutex = new Mutex(true, this.UniqueName, out __firstInstance);<br />
        }<br />
<br />
        // Disposing resources<br />
        ~SingleProgramInstance()<br />
        {            <br />
            this.Dispose();<br />
        }<br />
      <br />
        public bool IsFirstInstance<br />
        {<br />
            get { return __firstInstance; }<br />
        } <br />
        <br />
        public void Dispose()<br />
        {<br />
            if (this.IsFirstInstance && this.Mutex != null)<br />
            {<br />
                this.Mutex.ReleaseMutex();<br />
                this.Mutex = null;<br />
<br />
                GC.SuppressFinalize(this);<br />
            }            <br />
        }       <br />
    }<br />
<br />
class Program<br />
    {<br />
        static void Main(string[] args)<br />
        {<br />
            using (SingleProgramInstance spi = new SingleProgramInstance("zxy123"))<br />
            {<br />
                if (spi.IsFirstInstance)            <br />
                    Console.WriteLine("First Instance");               <br />
<br />
                else                <br />
                    Console.WriteLine("!!!!! NOT First Instance !!!!!!");              <br />
<br />
                spi.Dispose();<br />
            }<br />
<br />
            Console.ReadKey();<br />
<br />
            Process.Start("test73_Mutex.exe");<br />
        }<br />
    }<br />
<br />

this fails from time to time

zilo

led mike10-Oct-07 4:45

10-Oct-07 4:45

Zilo(svk) wrote:
this fails from time to time

Yes it would. The code in the main() method does not reflect the desired behavior as you described it in your original post. This would also be known as "a bug".

Stevo Z10-Oct-07 5:24

10-Oct-07 5:24

Can you be more specific ?

looks like I'll use your solution.

Anyway thank you very much!!!

led mike10-Oct-07 5:58

10-Oct-07 5:58

Zilo(svk) wrote:
looks like I'll use your solution.

Oh dear, that's why I don't normally post code. You should only use your solution. This requires your doing the work to understand what you are doing.

Zilo(svk) wrote:
Can you be more specific ?

Yes, here is what you said:

Zilo(svk) wrote:
I have an application and I want to keep only one instance running

The code in your main() method cannot possibly do that since you release the Mutex at the start of the application rather than right before it ends.

Also:

Zilo(svk) wrote:
I have an application and I want to keep only one instance running

Restarting the application from itself just doesn't make any sense. If you want an instance running and you already have an instance running then you have already satisfied that requirement so no action needs to be taken.

Stevo Z10-Oct-07 8:36

10-Oct-07 8:36

led mike wrote:
Oh dear, that's why I don't normally post code. You should only use your solution. This requires your doing the work to understand what you are doing.

I never use code only by copying it, that's not the way I work. I always try to understand it. That, of course, doesn't mean that I'm going to dig for every method I see in MSDN just to be 110% sure, that's a waste of time. I was satisfied with explanation in article where my code comes from, maybe I missed something ?!

led mike wrote:
The code in your main() method cannot possibly do that since you release the Mutex at the start of the application rather than right before it ends.

I release Mutex after all work is done, that means main application form and all application resources are disposed (which was not in that example to keep it simple), as I wrote in first post. After Mutex is released I can restart application in certain case (not always of course). Obviously I cannot run restarting sequence before Mutex is released.

led mike wrote:
Restarting the application from itself just doesn't make any sense. If you want an instance running and you already have an instance running then you have already satisfied that requirement so no action needs to be taken.

Restarting application makes exactly same sense as restarting windows for instance. When application starts, certain key resources are loaded, that may not be refreshed/reloaded while application runs (for simplicity reasons). I need to keep only one instance because using(modifying) those key resources by two application instances at one time would cause possible errors...

led mike10-Oct-07 8:51