HttpClient get JSON as AsyncEnumerable

A new extension method – GetFromJsonAsAsyncEnumerable<T> – has been added to the HttpClient part of .NET 8. This new method will take the response body JSON and deserialize it into an async enumerable operation.

The complete signature of the extension method is as follows:

[RequiresUnreferencedCode(HttpContentJsonExtensions.SerializationUnreferencedCodeMessage)]
[RequiresDynamicCode(HttpContentJsonExtensions.SerializationDynamicCodeMessage)]
public static IAsyncEnumerable<TValue?> GetFromJsonAsAsyncEnumerable<TValue>(
    this HttpClient client,
    [StringSyntax(StringSyntaxAttribute.Uri)] string? requestUri,
    CancellationToken cancellationToken = default) =>
    GetFromJsonAsAsyncEnumerable<TValue>(client, requestUri, options: null, cancellationToken);

Let’s take a look at how to use it. First thing to note is that the GetFromJsonAsAsyncEnumerable is not async, as the async part is being handled by the IAsyncEnumerable returned.

IAsyncEnumerable<Hotel> hotels = client.GetFromJsonAsAsyncEnumerable<Hotel>("https://foo.bar/api/hotels");

Next, we take the hotels result and use an await foreach to await and iterate on each element of the IAsyncEnumerable.

await foreach (var hotel in hotels)
{
    Console.WriteLine($"{hotel.stars}* | {hotel.name}");
}

Inside the body of the foreach you can do anything you want with your hotel. Full example below:

using System.Net.Http.Json;

using var client = new HttpClient();
IAsyncEnumerable<Hotel> hotels = client.GetFromJsonAsAsyncEnumerable<Hotel>("https://foo.bar/api/hotels");

await foreach (var hotel in hotels)
{
    Console.WriteLine($"{hotel.stars}* | {hotel.name}");
}

public record Hotel(string name, string address, int stars);