How do I specify the accepted response content types with HttpClient (C#)?

When using HttpClient in C#, you can specify the accepted response content types by setting the Accept header in the HttpRequestMessage or by adding to the DefaultRequestHeaders of the HttpClient instance.

Here is an example of how to specify accepted response content types for a single request using HttpRequestMessage:

using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (var client = new HttpClient())
        {
            // Create the HttpRequestMessage
            var request = new HttpRequestMessage(HttpMethod.Get, "http://example.com");

            // Add Accept header to specify the accepted response content types
            request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); // Accept JSON
            request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("text/plain")); // Accept plain text

            // Send the request
            var response = await client.SendAsync(request);

            if (response.IsSuccessStatusCode)
            {
                string content = await response.Content.ReadAsStringAsync();
                Console.WriteLine(content);
            }
            else
            {
                Console.WriteLine($"Error: {response.StatusCode}");
            }
        }
    }
}

If you want to set the accepted response content types for all requests made by an HttpClient instance, you can modify the DefaultRequestHeaders as shown below:

using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (var client = new HttpClient())
        {
            // Set the default Accept header to specify the accepted response content types
            client.DefaultRequestHeaders.Accept.Clear();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); // Accept JSON
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("text/plain")); // Accept plain text

            // Now all requests made with this client will use the specified Accept header
            var response = await client.GetAsync("http://example.com");

            if (response.IsSuccessStatusCode)
            {
                string content = await response.Content.ReadAsStringAsync();
                Console.WriteLine(content);
            }
            else
            {
                Console.WriteLine($"Error: {response.StatusCode}");
            }
        }
    }
}

In both examples, we specify that we want to accept application/json and text/plain as response content types. The MediaTypeWithQualityHeaderValue class is used to add values to the Accept header with an optional quality factor that indicates the preference for that media type.

Remember to always dispose of your HttpClient and HttpRequestMessage objects to free up resources, which is usually done with the using statement in C#. Also, for better performance and resource management, it is recommended to reuse a single HttpClient instance for multiple requests instead of creating a new one for each request.