For apps that target Windows Phone OS 7.0 and 7.1, do not use any members of this type in your app. If you do, your code will throw a MethodAccessException. This type is security-critical, which restricts it to internal use by the .NET Framework for Windows Phone class library.
Receives the error code, number of bytes, and overlapped value type when an I/O operation completes on the thread pool.
This API is not CLS-compliant.
public delegate void IOCompletionCallback(
Windows Phone OS
Supported in: 8.1, 8.0, 7.1, 7.0