Task cancellation

Cancellation is an optional thing for TAP-based asynchronous methods. If the method accepts the CancellationToken as the parameter, it can be used by the caller party to cancel a task. However, for a TAP, the cancellation should be properly handled. Here is a basic example showing how cancellation can be implemented:

static void Main(string[] args) 
{ 
  CancellationTokenSource tokenSource = new CancellationTokenSource(); 
  CancellationToken token = tokenSource.Token; 
  Task.Factory.StartNew(() => SaveFileAsync(path, bytes, token)); 
} 
 
static Task<int> SaveFileAsync(string path, byte[] fileBytes, CancellationToken cancellationToken) 
{ 
  if (cancellationToken.IsCancellationRequested) 
  { 
    Console.WriteLine("Cancellation is requested..."); 
    cancellationToken.ThrowIfCancellationRequested      
  } 
  //Do some file save operation 
  File.WriteAllBytes(path, fileBytes); 
  return Task.FromResult<int>(0); 
} 

In the preceding code, we have a SaveFileAsync method that takes the byte array and the CancellationToken as parameters. In the Main method, we initialize the CancellationTokenSource that can be used to cancel the asynchronous operation later in the program. To test the cancellation scenario, we will just call the Cancel method of the tokenSource after the Task.Factory.StartNew method and the operation will be canceled. Moreover, when the task is canceled, its status is set to Cancelled and the IsCompleted property is set to true.