ReaderWriterLockSlim.TryEnterReadLock Method (Int32)


Tries to enter the lock in read mode, with an optional integer time-out.

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

public bool TryEnterReadLock(
	int millisecondsTimeout


Type: System.Int32

The number of milliseconds to wait, or -1 (Timeout.Infinite) to wait indefinitely.

Return Value

Type: System.Boolean

true if the calling thread entered read mode, otherwise, false.

Exception Condition

The RecursionPolicy property is LockRecursionPolicy.NoRecursion and the current thread has already entered the lock.


The recursion number would exceed the capacity of the counter. The limit is so large that applications should never encounter it.


The value of millisecondsTimeout is negative, but it is not equal to Timeout.Infinite (-1), which is the only negative value allowed.


The ReaderWriterLockSlim object has been disposed.

If millisecondsTimeout is 0 (zero), this method checks the lock state and returns false immediately if the desired state is unavailable.

Multiple threads can enter read mode at the same time.

If one or more threads are waiting to enter write mode, a thread that calls the TryEnterReadLock method blocks until those threads have either timed out or entered write mode and then exited from it, or until the calling thread's own time-out interval expires.


If a lock allows recursion, a thread that has entered the lock in read mode can enter read mode recursively, even if other threads are waiting to enter write mode.

One thread can be in upgradeable mode while other threads are in read mode. If additional threads are waiting to enter upgradeable mode, and there are no threads waiting to enter write mode, threads that call the TryEnterReadLock method enter read mode immediately and do not block.

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
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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