An asynchronous method is a method that can return before it has finished executing. Any method that performs a potentially long-running task, such as accessing a web resource or reading a file, can be made asynchronous to improve the responsiveness of the program. This is especially important in graphical applications, because any method that takes a long time to execute on the user interface thread will cause the program to be unresponsive while waiting for that method to complete.
The Async and Await Keywords
Introduced in C# 5.0, the async and await keywords allow asynchronous methods ...
