Parallel Programming with Task Class

Run a long running operation on another thread

// waits for the task to complete because of "await" keyword
// control returns to the caller method while task executes
// code following Task.Run() executes after the task completes

// this is ideal for executing code from "click" 
// and event handlers in a GUI application for a
// responsive user experience

int retVal = await Task.Run(
() => 
{
// long running operation
return 1; 
}
);

Run two long running operations one after the other on another thread

// note how the second task uses the result from first task
retVal = await Task.Run(
() => { return 1;  }
).ContinueWith(t => { return 1 + t.Result; });

Communicate cancellation request to a Task

static CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
static CancellationToken cancellationToken = cancellationTokenSource.Token;

int retVal = await Task.Run(
() => 
{
// long running operation
if (cancellationToken.IsCancellationRequested)
     // OperationCanceledException is caught by the method
     // running the task and shown to user
cancellationToken.ThrowIfCancellationRequested();
return 1; 
}, cancellationToken
);

To cancel:
CancellationTokenSource.Cancel();

Report Progress

//  This lambda will be run on the UI thread.

var progress = new Progress<string>(msg =>

{

  textBox.Text = msg;

});

// "progress" is passed as IProgress<string> progress to the

// long running method so that

// it can report progress

Block execution until a task completes

Task<int> task = Task.Run(
() =>
{
// long running operation
return 1;
}
);

// Halt further execution until the task completes
Task.WaitAll(task);

// See the "await" examples above. With "await" the execution
// returns to the caller while a task runs