CatalogClient.cs

using System.Net.Http.Json;
using HttpQueryDemo.Contracts;

namespace HttpQueryDemo.Client;

/// <summary>
/// A typed <c>HttpClient</c> wrapper that talks to the catalogue API using the
/// HTTP <c>QUERY</c> method. Registered through <c>IHttpClientFactory</c>, so it
/// gets connection pooling and a resilience pipeline for free.
/// </summary>
public sealed class CatalogClient(HttpClient http)
{
    /// <summary>
    /// Runs a product search by sending the query in the body of an HTTP QUERY
    /// request — the client-side counterpart of the server's endpoint.
    /// </summary>
    public async Task<ProductQueryResult> QueryAsync(
        ProductQuery query, CancellationToken cancellationToken = default)
    {
        // HttpMethod.Query is the first-class QUERY verb introduced in .NET 10.
        // Before .NET 10 you'd write new HttpMethod("QUERY") — same wire result.
        using var request = new HttpRequestMessage(HttpMethod.Query, "products/query")
        {
            Content = JsonContent.Create(query, options: ProductJson.Options),
        };

        using var response = await http.SendAsync(request, cancellationToken);
        response.EnsureSuccessStatusCode();

        var result = await response.Content
            .ReadFromJsonAsync<ProductQueryResult>(ProductJson.Options, cancellationToken);

        return result ?? throw new InvalidOperationException("The API returned an empty body.");
    }
}