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Class SystemLock

Provides a synchronization lock that can be either local (anonymous) or system-wide (named).

Inheritance

object

Namespace: Umbraco.Cms.Core

Assembly: Umbraco.Core.dll

Syntax

public class SystemLock

Remarks

This is NOT a reader/writer lock and is NOT a recursive lock.

Uses a named Semaphore instead of a Mutex because mutexes have thread affinity which does not work with async situations.

It is important that managed code properly releases the Semaphore before going down, otherwise it will maintain the lock. However, when the whole process (w3wp.exe) goes down and all handles to the Semaphore have been closed, the Semaphore system object is destroyed - so an iisreset should clean up everything.

See https://devblogs.microsoft.com/pfxteam/building-async-coordination-primitives-part-6-asynclock/

Constructors

SystemLock()

Initializes a new instance of the SystemLock class with an anonymous (local) semaphore.

Declaration

public SystemLock()

SystemLock(string?)

Initializes a new instance of the SystemLock class.

Declaration

public SystemLock(string? name)

Parameters

Type	Name	Description
string	name	The name of the system-wide semaphore, or null for an anonymous local semaphore.

Methods

Lock()

Acquires the lock, blocking until the lock is available.

Declaration

public IDisposable? Lock()

Returns

Type	Description
IDisposable	An System.IDisposable that releases the lock when disposed.

Lock(int)

Acquires the lock, blocking until the lock is available or the timeout expires.

Declaration

public IDisposable? Lock(int millisecondsTimeout)

Parameters

Type	Name	Description
int	millisecondsTimeout	The maximum time in milliseconds to wait for the lock.

Returns

Type	Description
IDisposable	An System.IDisposable that releases the lock when disposed.

Exceptions

Type	Condition
TimeoutException	The lock could not be acquired within the timeout period.