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Overlapped.Pack Method (IOCompletionCallback)

Note: This API is now obsolete. The non-obsolete alternative is Pack.

Packs the current instance into a NativeOverlapped structure, specifying the delegate to be invoked when the asynchronous I/O operation is complete.

This API is not CLS-compliant. 

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

[ObsoleteAttribute("This method is not safe.  Use Pack (iocb, userData) instead.  http://go.microsoft.com/fwlink/?linkid=14202")]
public NativeOverlapped* Pack(
	IOCompletionCallback iocb


Type: System.Threading.IOCompletionCallback

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

Return Value

Type: System.Threading.NativeOverlapped*
An unmanaged pointer to a NativeOverlapped structure.


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.

Important noteImportant

The caller is responsible for pinning the buffer. If the application domain is unloaded, however, the handle to the pinned buffer is destroyed and the buffer is released, leaving the I/O operation to write to the freed address. For this reason, it is better to use the Pack(IOCompletionCallback, Object) method overload, in which the runtime pins the buffer.

.NET Framework

Supported in: 1.1, 1.0
Obsolete (compiler warning) in 4.5
Obsolete (compiler warning) in 4.5.1
Obsolete (compiler warning) in 4.5.2
Obsolete (compiler warning) in 4
Obsolete (compiler warning) in 3.5
Obsolete (compiler warning) in 3.5 SP1
Obsolete (compiler warning) in 3.0
Obsolete (compiler warning) in 3.0 SP1
Obsolete (compiler warning) in 3.0 SP2
Obsolete (compiler warning) in 2.0
Obsolete (compiler warning) in 2.0 SP1
Obsolete (compiler warning) in 2.0 SP2

.NET Framework Client Profile

Obsolete (compiler warning) in 4
Obsolete (compiler warning) in 3.5 SP1

  • SecurityCriticalAttribute 

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

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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