Implementing TAP using compilers

Any method that is attributed with the async keyword (for C#) or Async for (Visual Basic) is called an asynchronous method. The async keyword can be applied to a method, anonymous method, or a Lambda expression, and the language compiler can execute that task asynchronously.

Here is a simple implementation of the TAP method using the compiler approach:

static void Main(string[] args) 
{ 
  var t = ExecuteLongRunningOperationAsync(100000); 
  Console.WriteLine("Called ExecuteLongRunningOperationAsync method, 
  now waiting for it to complete"); 
  t.Wait(); 
  Console.Read(); 
}   
 
public static async Task<int> ExecuteLongRunningOperationAsync(int millis) 
{ 
  Task t = Task.Factory.StartNew(() => RunLoopAsync(millis)); 
  await t; 
  Console.WriteLine("Executed RunLoopAsync method"); 
  return 0; 
} 
 
public static void RunLoopAsync(int millis) 
{ 
  Console.WriteLine("Inside RunLoopAsync method"); 
  for(int i=0;i< millis; i++) 
  {

    Debug.WriteLine($"Counter = {i}"); 
  } 
  Console.WriteLine("Exiting RunLoopAsync method"); 
} 

In the preceding code, we have the ExecuteLongRunningOperationAsync method, which is implemented as per the compiler approach. It calls the RunLoopAsync that executes a loop for a certain number of milliseconds that is passed in the parameter. The async keyword on the ExecuteLongRunningOperationAsync method actually tells the compiler that this method has to be executed asynchronously, and, once the await statement is reached, the method returns to the Main method that writes the line on a console and waits for the task to be completed. Once the RunLoopAsync is executed, the control comes back to await and starts executing the next statements in the ExecuteLongRunningOperationAsync method.