{"id":2046,"date":"2018-07-04T12:22:00","date_gmt":"2018-07-04T11:22:00","guid":{"rendered":"https:\/\/www.autoitconsulting.com\/site\/?p=2046"},"modified":"2025-07-26T09:27:40","modified_gmt":"2025-07-26T08:27:40","slug":"single-instance-winform-app-csharp-mutex-named-pipes","status":"publish","type":"post","link":"https:\/\/www.autoitconsulting.com\/site\/development\/single-instance-winform-app-csharp-mutex-named-pipes\/","title":{"rendered":"Single Instance WinForm App in C# with Mutex and Named Pipes"},"content":{"rendered":"\n

Overview<\/h2>\n\n\n\n

This post shows how to create a single instance WinForm C# application using a Mutex. It also demonstrates how to send any object between instances with Named Pipes.<\/p>\n\n\n\n

While writing OSD Background<\/a> I wanted an application that would only allow a single instance to run at any given time. In addition I wanted it so that if another instance was executed with different parameters – or a quit request – then those parameters would be sent to the original instance so that it could process them. After sending the parameters the second instance would terminate.<\/p>\n\n\n\n

The final solution I came up with uses a Mutex<\/a> to handle the single instancing. The information I wanted to send between instances is wrapped into a ‘payload’ object that is serialized<\/a> into XML and sent over a Named Pipe<\/a>.<\/p>\n\n\n\n

Downloads<\/h2>\n\n\n\n

A fully working example can be downloaded from GitHub at https:\/\/github.com\/AutoItConsulting\/examples-csharp\/tree\/master\/MutexSingleInstanceAndNamedPipe
\"Download<\/a><\/p>\n\n\n\n

On first run the application shows a simple WinForm application with an empty text box. When another attempt is made to run the application the command-line parameters are sent via a Named Pipe to the first instance and shown in the text box.<\/p>\n\n\n\n

Single Instance Using a Mutex<\/h2>\n\n\n\n

Mutex is a simple object, you just pick a unique instance name and create a new object. A bool is returned that allows you to test if this mutex is owned by just the current process or if it is already in use. As long as the mutex is referenced other processes that request a new Mutex object will be able to see that another instance is running. In the code below I request the Mutex in the form Load event, and release it in the form Close event.<\/p>\n\n\n\n

Note:<\/strong> It is critical to reference the Mutex object right at the end of your program’s execution rather than relying on the garbage collector to clean up after your program exits. Otherwise in a release<\/strong> build the compiler is clever enough to see that after your initial creation of the Mutex object you never use it again and will signal for it to be disposed before<\/strong> your program has exited. Of course, Mutex implements the IDisposable<\/strong> interface so it’s good practice to explicitly dispose it anyway. This explicit dispose in the Form Close event is enough to prevent the compiler from automatically disposing the Mutex earlier.<\/p>\n\n\n\n

Here are the relevant functions:<\/p>\n\n\n\n

C#<\/span><\/span>