C# and .NET Framework (4.5 & Core) supports asynchronous programming using some native functions, classes, and reserved keywords.
Before we see what is asynchronous programming, let's understand what is synchronous programming using the following console example.
In the above example, the
LongProcess() method is some long-running task such as reading a file from the server, calling a web API that returns a large amount of data or uploading or downloading a big file. It takes a little longer time to execute (Thread.Sleep(4000) holds it for 4 seconds just to show long execution time). The ShortProcess() is a simple method that gets executed after the LongProcess() method.The above program executes synchronously. It means execution starts from the
Main() method wherein it first executes the LongProcess() method and then ShortProcess() method. During the execution, an application gets blocked and becomes unresponsive (You can see this in Windows-based applications mainly). This is called synchronous programming where execution does not go to next line until the current line executed completely.