The asynchronous programming model pattern

The asynchronous programming model (APM) is an asynchronous operation that uses the IAsyncResult interface as its design pattern. It's also called the IAsyncResult pattern. For this purpose, the framework has provided the method named BeginXx and EndXx, in which Xx is the operation name, for instance, BeginRead and EndRead provided by the FileStream class to read bytes from a file asynchronously.

The difference in the synchronous Read() method with BeginRead() and EndRead() can be recognized from the method's declaration, as follows:

public int Read( 
  byte[] array, 
  int offset, 
  int count 
) 
public IAsyncResult BeginRead( 
  byte[] array, 
  int offset, 
  int numBytes, 
  AsyncCallback userCallback, 
  object stateObject 
) 
public int EndRead( 
  IAsyncResult asyncResult 
) 

As we can see, in the synchronous Read() method, we need three parameters; they are array,...