Begins an asynchronous request to get the modification time for a remote file.
An IAsyncResult that references the asynchronous get.
You can create a callback method that implements the AsyncCallback delegate and pass its name to the BeginGetLastWriteTime method. The state argument may be used to pass in data that will be passed to the callback method.
For more information please refer to the synchronous version of this method, GetLastWriteTime.