Cancellation Token Provider

A CancellationToken enables cooperative cancellation between threads, thread pool work items, or Task objects. To handle the possible cancellation of the operation, VCP provides ICancellationTokenProvider to obtain the CancellationToken itself from the source.

To get more information about CancellationToken, see Microsoft Documentation.

ICancellationTokenProvider

ICancellationTokenProvider is an abstraction to provide CancellationToken for different scenarios.

Generally, you should pass the CancellationToken as a parameter for your method to use it. With the ICancellationTokenProvider you don't need to pass CancellationToken for every method. ICancellationTokenProvider can be injected with the dependency injection and provides the token from it's source.

Example:

using System.Threading.Tasks;
using Verto.Vcp.DependencyInjection;
using Verto.Vcp.Threading;

namespace MyProject
{
    public class MyService : ITransientDependency
    {
        private readonly ICancellationTokenProvider _cancellationTokenProvider;

        public MyService(ICancellationTokenProvider cancellationTokenProvider)
        {
            _cancellationTokenProvider = cancellationTokenProvider;
        }

        public async Task DoItAsync()
        {
            while (_cancellationTokenProvider.Token.IsCancellationRequested == false)
            {
                // ...
            }
        }
    }
}

Built-in providers

• NullCancellationTokenProvider

  The NullCancellationTokenProvider is a built in provider and it supply always CancellationToken.None.

• HttpContextCancellationTokenProvider

  The HttpContextCancellationTokenProvider is a built in default provider for VCP Web applications. It simply provides a CancellationToken that is source of the web request from the HttpContext.

Implementing the ICancellationTokenProvider

You can easily create your CancellationTokenProvider by creating a class that implements the ICancellationTokenProvider interface, as shown below:

using System.Threading;

namespace VcpDemo
{
    public class MyCancellationTokenProvider : ICancellationTokenProvider
    {
        public CancellationToken Token { get; }

        private MyCancellationTokenProvider()
        {

        }
    }
}