C# 1001 notes

​​Foreach Loop in C# (part 4)



Beginning with C# 8.0, you can use the await foreach statement to consume an asynchronous stream of data, that is, the collection type that implements the IAsyncEnumerable<T> interface. Each iteration of the loop may be suspended while the next element is retrieved asynchronously. The following example shows how to use the await foreach statement:



You can also use the await foreach statement with an instance of any type that satisfies the following conditions:



🔸 A type has the public parameterless GetAsyncEnumerator method. That method can be a type's extension method.



🔸 The return type of the GetAsyncEnumerator method has the public Current property and the public parameterless MoveNextAsync method whose return type is Task<bool>, ValueTask<bool>, or any other awaitable type whose awaiter's GetResult method returns a bool value.



By default, stream elements are processed in the captured context. If you want to disable capturing of the context, use the TaskAsyncEnumerableExtensions.ConfigureAwait extension method. For more information about synchronization contexts and capturing the current context, see Consuming the Task-based asynchronous pattern. For more information about asynchronous streams, see the Asynchronous streams section of the What's new in C# 8.0 article.



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