Using The New IAsyncEnumerable Interface In .NET Core 3

Introduction

The IAsyncEnumerable<T> interface in .NET Core (and later versions, including .NET 5 and beyond) is designed to represent a sequence of asynchronous values. It is similar to the traditional IEnumerable<T> interface, but it allows you to work with asynchronous data streams in a more efficient and convenient way. This is particularly useful when dealing with asynchronous operations, such as querying a database or fetching data over the network.

Here’s a basic example of how to use the IAsyncEnumerable<T> interface in .NET Core 5:

1. Define an Asynchronous Data Source:
   First, you need to define a method that returns an IAsyncEnumerable<T>. This method will serve as your asynchronous data source. For example, let’s say you have an asynchronous operation to fetch data from a database:

   public async IAsyncEnumerable<string> GetDataAsync()
   {
       // Simulate fetching data asynchronously
       for (int i = 0; i < 10; i++)
       {
           await Task.Delay(100); // Simulate async operation
           yield return $"Item {i}";
       }
   }

2. Consuming the Asynchronous Data:
   You can consume the asynchronous data using the await foreach syntax:

   await foreach (var item in GetDataAsync())
   {
       Console.WriteLine(item);
   }

In this example, each item will be processed asynchronously as it becomes available, and the loop won’t block the thread.

3. Cancellation and Error Handling:
   IAsyncEnumerable<T> supports cancellation using the CancellationToken parameter, similar to other asynchronous operations in .NET. Additionally, you can use try-catch blocks to handle errors.

   await foreach (var item in GetDataAsync().WithCancellation(cancellationToken))
   {
       try
       {
           // Process item
       }
       catch (Exception ex)
       {
           // Handle error
       }
   }

The IAsyncEnumerable<T> interface simplifies working with asynchronous data streams and improves the efficiency of asynchronous data processing by allowing items to be processed as soon as they become available, rather than waiting for the entire collection to be fetched.

Remember that support for asynchronous sequences using IAsyncEnumerable<T> is not limited to consuming data. It can also be used to produce data asynchronously, enabling you to create efficient and asynchronous data pipelines within your .NET Core applications.