Monitor.TryEnter Method (Object, TimeSpan)


Attempts, for the specified amount of time, to acquire an exclusive lock on the specified object.

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

public static bool TryEnter(
	object obj,
	TimeSpan timeout


Type: System.Object

The object on which to acquire the lock.

Type: System.TimeSpan

A TimeSpan representing the amount of time to wait for the lock. A value of –1 millisecond specifies an infinite wait.

Return Value

Type: System.Boolean

true if the current thread acquires the lock; otherwise, false.

Exception Condition

The obj parameter is null.


The value of timeout in milliseconds is negative and is not equal to Infinite (–1 millisecond), or is greater than MaxValue.

If the value of the timeout parameter converted to milliseconds equals –1, this method is equivalent to Enter. If the value of timeout equals 0, this method is equivalent to TryEnter.


Use Monitor to lock objects (that is, reference types), not value types. For details, see the Monitor class topic.

To ensure that the thread does not enter the critical section, you should examine the method's return value and execute code in the critical section only if its return value is true. The following code fragment shows the pattern used to call this method. Note that you should call Exit in a finally block to ensure that the calling thread releases its lock on the critical section if an exception occurs.

var lockObj = new Object();
var timeout = TimeSpan.FromMilliseconds(500);

if (Monitor.TryEnter(lockObj, timeout)) {
   try {
      // The critical section.
   finally {
      // Ensure that the lock is released.
else {
   // The lock was not acquired.

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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