Overlapped.Pack Method (IOCompletionCallback, Object)


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Packs the current instance into a NativeOverlapped structure, specifying a delegate that is invoked when the asynchronous I/O operation is complete and a managed object that serves as a buffer.

This API is not CLS-compliant.

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

public unsafe NativeOverlapped* Pack(
	IOCompletionCallback iocb,
	object userData


Type: System.Threading.IOCompletionCallback

An IOCompletionCallback delegate that represents the callback method invoked when the asynchronous I/O operation completes.

Type: System.Object

An object or array of objects representing the input or output buffer for the operation. Each object represents a buffer, for example an array of bytes.

Return Value

Type: System.Threading.NativeOverlapped*

An unmanaged pointer to a NativeOverlapped structure.

Exception Condition

The current Overlapped has already been packed.

The unmanaged pointer returned by this method can be passed to the operating system in overlapped I/O operations. The NativeOverlapped structure is fixed in physical memory until Unpack is called.

The buffer or buffers specified in userData must be the same as those passed to the unmanaged operating system function that performs the asynchronous I/O.


The runtime pins the buffer or buffers specified in userData for the duration of the I/O operation. If the application domain is unloaded, the runtime keeps the memory pinned until the I/O operation completes.


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

.NET Framework
Available since 2.0
Available since 2.0
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