.NET Questions

Hi i have written a small utility program using c# when user clicks the exe as many times the new instances of the application get created what if i want the user to limit to use only one instance application at a time.... is there any way i can achieve it in C#..

Thankyou,

In terms of pure Win32 API you can use the CreateMutex Win32 API and use GetLastError to check for ERROR_ALREADY_EXISTS to detect any previous running instance.

Thankyou jussi :)

I Got this ex whic works fine

http://www.codeproject.com/useritems/csharponeinst.asp?df=100&forumid=270354&exp=0&select=1377873

Sells' book has something on this, the relevant part of which is fortunately online:

http://www.awprofessional.com/articles/article.asp?p=474650&seqNum=2&rl=1

Never done it before though.

System.Threading.Mutex

See Also:
http://www.yoda.arachsys.com/csharp/faq/#one.application.instance

Snippet:
bool firstInstance;
Mutex mutex = new Mutex(false, "Local\\"+someUniqueName, out firstInstance);
// If firstInstance is now true, we're the first instance of the application;
// otherwise another instance is running.

Which version of the CLR are you using? WinForms 2.0 has support for single instance apps built in.

Only for Visual Basic applications, though.

Of course, you could always create a single-instance VB .NET project that runs your C# code.

Chris, did you read it? The example is written in C#, you just add a reference to Microsoft.VisualBasic.dll, part of the .NET install.

You're right, judging by Sells' example it looks simple enough to use this functionality from C#.  The MSDN Library pages I found were talking about a VB project setting, that's why I thought it was an "exclusive" feature.

He does say he doesn't understand why the functionality wasn't added to the main framework (one of the notes, had to check in the book to find it). Although the dll is part of the distribution.

http://www.codeproject.com/csharp/singleinstance.asp


Guyyzzzzzzzzzzzzzz this is the superb example which works very fine check it out :)

Just remember, if you use a global atom, as the code project article suggests, if the program crashes the user will not be able to restart the application until they restart the computer and clear the globla atom.

But if you use a Mutex this is never a problem since windows will automatically release the mutex should the application crash.