Mutex.TryOpenExisting Method (String, Mutex)

.NET Framework (current version)

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Opens the specified named mutex, if it already exists, and returns a value that indicates whether the operation succeeded.

Namespace:   System.Threading
Assembly:  mscorlib (in mscorlib.dll)

public static bool TryOpenExisting(
	string name,
	out Mutex result


Type: System.String

The name of the system mutex to open.

Type: System.Threading.Mutex

When this method returns, contains a Mutex object that represents the named mutex if the call succeeded, or null if the call failed. This parameter is treated as uninitialized.

Return Value

Type: System.Boolean

true if the named mutex was opened successfully; otherwise, false.

Exception Condition

name is an empty string.


name is longer than 260 characters.


name is null.


A Win32 error occurred.


The named mutex exists, but the user does not have the security access required to use it.

If the named mutex does not exist, this method does not create it. To create the system mutex when it does not already exist, use one of the Mutex constructors that has a name parameter.

If you are uncertain whether a named mutex exists, use this method overload instead of the OpenExisting(String) method overload, which throws an exception if the mutex does not exist.

Multiple calls to this method that use the same value for name do not necessarily return the same Mutex object, even though the objects that are returned represent the same named system mutex.

This method overload is equivalent to calling the TryOpenExisting(String, MutexRights, Mutex) method overload and specifying MutexRights.Synchronize and MutexRights.Modify rights, combined by using the bitwise OR operation. Specifying the MutexRights.Synchronize flag allows a thread to wait on the mutex, and specifying the MutexRights.Modify flag allows a thread to call the ReleaseMutex method.

This method does not request ownership of the mutex.


requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.5
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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