Implementing asynchronous interfaces

In this article, we will be discussing how to define an async interface based on a synchronous interface example.

Introduction

Async interfaces are useful when you need to perform asynchronous operations within your application. Async interfaces allow you to define methods that return a Task object instead of a value, allowing you to use the await keyword to asynchronously wait for the operation to complete.

One important aspect of async programming is the ability to cancel an async operation. This is particularly useful in scenarios where the async operation may take a long time to complete, or when the operation is no longer needed. To support cancellation in async operations, you can use a cancellation token.

Step 1: Define the Synchronous Interface

The first step in defining an async interface is to define the synchronous version of the interface. This will serve as the basis for the async interface.

Here is an example of a synchronous interface:

public interface IDataProcessor
{
    void ProcessData(IEnumerable<IData> data);
}

This interface has a single method, ProcessData, which takes an IEnumerable of IData objects as input and processes the data.

Step 2: Define the Async Interface

Now that we have defined the synchronous interface, we can define the async version of the interface. To do this, we simply need to modify the ProcessData method to return a Task object instead of void, and add the async keyword to the method.

Here is the async version of the IDataProcessorAsync interface:

public interface IDataProcessorAsync
{
    Task ProcessDataAsync(IEnumerable<IData> data, CancellationToken cancellationToken);
}

In this version of the interface, we have added a cancellationToken parameter to the ProcessDataAsync method. This parameter is of type CancellationToken, which is a struct that represents a cancellation request.

Step 3: Implement the Async Interface

Now that we have defined the async version of the interface, we can implement it in a class. To implement the async interface, we simply need to define a method that matches the signature of the ProcessDataAsync method and uses the await keyword to asynchronously perform the data processing.

Here is an example of an async implementation of the IDataProcessorAsync interface:

public class DataProcessor : IDataProcessorAsync
{
    public async Task ProcessDataAsync(IEnumerable<IData> data, CancellationToken cancellationToken)
    {
        // Process the data asynchronously
        await Task.Delay(1000, cancellationToken);
    }
}

This implementation has a single method, ProcessDataAsync, which takes an IEnumerable of IData objects and a cancellationToken as input and asynchronously processes the data. In this example, the data processing is simulated using the Task.Delay method, which causes the task to wait for a specified amount of time before completing. The cancellationToken is passed to the Task.Delay method as an argument, allowing the task to be cancelled if a cancellation request is made.

Step 4: Use the Async Interface

Now that we have defined and implemented the async interface, we can use it in our application. To use the async interface, we simply need to create an instance of the implementing class and call the async method using the await keyword.

Here is an example of how to use the async IDataProcessor interface:

var cts = new CancellationTokenSource();
var dataProcessor = new DataProcessor();
await dataProcessor.ProcessDataAsync(data, cts.Token);

This code creates a CancellationTokenSource object, which is used to create and manage a cancellation token. The cts.Token property is then passed to the ProcessDataAsync method as a cancellation token. The await keyword is used to asynchronously wait for the data processing to complete.

To cancel the async operation, you can call the Cancel method on the CancellationTokenSource object. This will trigger a cancellation request, which will cause the ProcessDataAsync method to throw a TaskCanceledException when the await keyword is encountered.

cts.Cancel();

Conclusion

In this article, we discussed how to define an async interface based on a synchronous interface example, including the use of a cancellation token. We defined the synchronous version of the interface, modified it to include a cancellation token and return a Task object, implemented the async interface in a class, and demonstrated how to use your new async interface implementation.