The IAsyncResult interface is implemented by classes containing methods that can operate asynchronously. It is the return type of methods that initiate an asynchronous operation, such as System.IO.FileStream.BeginRead(Byte[], int, int, AsyncCallback, object), and it is passed to methods that conclude an asynchronous operation, such as System.IO.FileStream.EndRead(IAsyncResult). IAsyncResult objects are also passed to methods invoked by AsyncCallback delegates when an asynchronous operation completes.

An object that supports the IAsyncResult interface stores state information for an asynchronous operation and provides a synchronization object to allow threads to be signaled when the operation completes.

For a detailed description of how the IAsyncResult interface is used, see the Calling Synchronous Methods Asynchronously topic.