ThreadPool.UnsafeQueueUserWorkItem Method (WaitCallback, Object)


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Queues the specified delegate to the thread pool, but does not propagate the calling stack to the worker thread.

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

public static bool UnsafeQueueUserWorkItem(
	WaitCallback callBack,
	object state


Type: System.Threading.WaitCallback

A WaitCallback that represents the delegate to invoke when a thread in the thread pool picks up the work item.

Type: System.Object

The object that is passed to the delegate when serviced from the thread pool.

Return Value

Type: System.Boolean

true if the method succeeds; OutOfMemoryException is thrown if the work item could not be queued.

Exception Condition

The caller does not have the required permission.


An out-of-memory condition was encountered.


The work item could not be queued.


callBack is null.

Unlike the QueueUserWorkItem method, UnsafeQueueUserWorkItem does not propagate the calling stack to the worker thread. This allows code to lose the calling stack and thereby to elevate its security privileges.


Using UnsafeQueueUserWorkItem could inadvertently open up a security hole. Code access security bases its permission checks on the permissions of all the callers on the stack. When work is queued on a thread pool thread using UnsafeQueueUserWorkItem, the stack of the thread pool thread will not have the context of the actual callers. Malicious code might be able exploit this to avoid permission checks.


Requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

.NET Framework
Available since 1.1
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