IOCompletionCallback Delegate

IOCompletionCallback Delegate

Receives the error code, number of bytes, and overlapped value type when an I/O operation completes on the thread pool.

This delegate is not CLS-compliant.  

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

public delegate void IOCompletionCallback (
	uint errorCode,
	uint numBytes,
	NativeOverlapped* pOVERLAP
Not applicable.



The error code.


The number of bytes that are transferred.


A NativeOverlapped representing an unmanaged pointer to the native overlapped value type.

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

Community Additions

© 2015 Microsoft