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Monitor.TryEnter Method (Object, Int32, Boolean%)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Attempts, for the specified number of milliseconds, to acquire an exclusive lock on the specified object, and atomically sets a value that indicates whether the lock was taken.

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

public static void TryEnter(
	Object obj,
	int millisecondsTimeout,
	ref bool lockTaken
)

Parameters

obj
Type: System.Object
The object on which to acquire the lock.
millisecondsTimeout
Type: System.Int32
The number of milliseconds to wait for the lock.
lockTaken
Type: System.Boolean %
The result of the attempt to acquire the lock, passed by reference. The input must be false. The output is true if the lock is acquired; otherwise, the output is false. The output is set even if an exception occurs during the attempt to acquire the lock.

ExceptionCondition
ArgumentException

The input to lockTaken is true.

ArgumentNullException

The obj parameter is null.

ArgumentOutOfRangeException

millisecondsTimeout is negative, and not equal to Infinite.

If the millisecondsTimeout parameter equals Infinite, this method is equivalent to Enter(Object). If millisecondsTimeout equals 0, this method is equivalent to TryEnter(Object).

If the lock was not taken because an exception was thrown, the variable specified for the lockTaken parameter is false after this method ends. This allows the program to determine, in all cases, whether it is necessary to release the lock.

NoteNote:

Use Monitor to lock objects (that is, reference types), not value types. For more information, see Enter and the conceptual topic Monitors.

The following code shows the basic pattern for using the TryEnter(Object, Boolean) method overload. This overload always sets the value of the variable that is passed to the ref parameter (ByRef in Visual Basic) lockTaken, even if the method throws an exception, so the value of the variable is a reliable way to test whether the lock has to be released.


bool acquiredLock = false;

try
{
    Monitor.TryEnter(lockObject, 500, ref acquiredLock);
    if (acquiredLock)
    {

        // Code that accesses resources that are protected by the lock.

    }
    else
    {

        // Code to deal with the fact that the lock was not acquired.

    }
}
finally
{
    if (acquiredLock)
    {
        Monitor.Exit(lockObject);
    }
}


Windows Phone OS

Supported in: 8.1, 8.0, 7.1

Windows Phone

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