Monitor.TryEnter Method (Object, Int32)


Attempts, for the specified number of milliseconds, to acquire an exclusive lock on the specified object.

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

Public Shared Function TryEnter (
	obj As Object,
	millisecondsTimeout As Integer
) As Boolean


Type: System.Object

The object on which to acquire the lock.

Type: System.Int32

The number of milliseconds to wait for the lock.

Return Value

Type: System.Boolean

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

Exception Condition

The obj parameter is null.


millisecondsTimeout is negative, and not equal to Infinite.

If the millisecondsTimeout parameter equals Infinite, this method is equivalent to Enter. If millisecondsTimeout 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 article.

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.

Dim lockObj As New Object()
Dim timeout As Integer = 500

If Monitor.TryEnter(lockObj, timeout) Then
      ' The critical section.
      ' Ensure that the lock is released.
   End Try
   ' The lock was not acquired.
End If

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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