LockRecursionPolicy Enumeration

July 28, 2014

Specifies whether a lock can be entered multiple times by the same thread.

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

public enum LockRecursionPolicy

Member nameDescription
NoRecursionIf a thread tries to enter a lock recursively, an exception is thrown. Some classes may allow certain recursions when this setting is in effect.
SupportsRecursionA thread can enter a lock recursively. Some classes may restrict this capability.

The default recursion policy depends on the type of lock. For the default policy and the precise behavior of lock recursion for any given lock type, see the documentation for the type. For example, the ReaderWriterLockSlim class does not allow a thread to enter the lock in write mode if it already entered the lock in read mode, regardless of the lock policy setting, in order to reduce the chance of deadlocks.

Currently only one lock uses this enumeration:

The following example shows two exception scenarios, one that depends on the LockRecursionPolicy setting and one that does not.

In the first scenario, the thread enters the lock in read mode and then tries to enter read mode recursively. If the ReaderWriterLockSlim is created by using the default constructor, which sets recursion policy to NoRecursion, an exception is thrown. If SupportsRecursion is used to create the ReaderWriterLockSlim, no exception is thrown.

In the second scenario, the thread enters the lock in read mode and then tries to enter the lock in write mode. LockRecursionException is thrown regardless of the lock recursion policy.

Windows Phone OS

Supported in: 8.1, 8.0

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