Parameters
- buffer
 - The buffer to read the data into.
 - offset
 - The byte offset in buffer at which to begin writing data read from the stream.
 - count
 - The maximum number of bytes to read.
 - callback
 - An optional asynchronous callback, to be called when the read is complete.
 - state
 - A user-provided object that distinguishes this particular asynchronous read request from other requests.
 
Return Value
An System.IAsyncResult that represents the asynchronous read, which could still be pending.