How do I send a PUT request using HttpClient (C#)?

The HttpClient class in C# provides a powerful way to send HTTP requests and handle responses. Here's a comprehensive guide on sending PUT requests using HttpClient.

Basic PUT Request with JSON Data

using System;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;

public class Program
{
    static async Task Main(string[] args)
    {
        var url = "https://api.example.com/users/123";

        var userData = new
        {
            Name = "John Doe",
            Email = "john.doe@example.com",
            Age = 30
        };

        var jsonContent = JsonSerializer.Serialize(userData);
        var content = new StringContent(jsonContent, Encoding.UTF8, "application/json");

        using var client = new HttpClient();

        try
        {
            var response = await client.PutAsync(url, content);
            response.EnsureSuccessStatusCode();

            var responseBody = await response.Content.ReadAsStringAsync();
            Console.WriteLine($"Success: {responseBody}");
        }
        catch (HttpRequestException ex)
        {
            Console.WriteLine($"Request error: {ex.Message}");
        }
    }
}

PUT Request with Custom Headers

using var client = new HttpClient();

// Add custom headers
client.DefaultRequestHeaders.Add("User-Agent", "MyApp/1.0");
client.DefaultRequestHeaders.Add("Authorization", "Bearer your-token-here");

var content = new StringContent(jsonData, Encoding.UTF8, "application/json");
var response = await client.PutAsync(url, content);

PUT Request with Form Data

var formData = new List<KeyValuePair<string, string>>
{
    new("name", "John Doe"),
    new("email", "john@example.com"),
    new("age", "30")
};

var content = new FormUrlEncodedContent(formData);
var response = await client.PutAsync(url, content);

PUT Request with File Upload

using var content = new MultipartFormDataContent();

// Add text fields
content.Add(new StringContent("John Doe"), "name");
content.Add(new StringContent("john@example.com"), "email");

// Add file
var fileContent = new ByteArrayContent(File.ReadAllBytes("profile.jpg"));
fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("image/jpeg");
content.Add(fileContent, "avatar", "profile.jpg");

var response = await client.PutAsync(url, content);

Best Practices with IHttpClientFactory

For production applications, use IHttpClientFactory to avoid socket exhaustion:

// In Startup.cs or Program.cs
services.AddHttpClient();

// In your service class
public class ApiService
{
    private readonly HttpClient _httpClient;

    public ApiService(IHttpClientFactory httpClientFactory)
    {
        _httpClient = httpClientFactory.CreateClient();
    }

    public async Task<bool> UpdateUserAsync(int userId, object userData)
    {
        var url = $"https://api.example.com/users/{userId}";
        var jsonContent = JsonSerializer.Serialize(userData);
        var content = new StringContent(jsonContent, Encoding.UTF8, "application/json");

        try
        {
            var response = await _httpClient.PutAsync(url, content);
            return response.IsSuccessStatusCode;
        }
        catch (HttpRequestException)
        {
            return false;
        }
    }
}

Error Handling and Status Code Checking

var response = await client.PutAsync(url, content);

switch (response.StatusCode)
{
    case HttpStatusCode.OK:
        var result = await response.Content.ReadAsStringAsync();
        Console.WriteLine($"Updated successfully: {result}");
        break;
    case HttpStatusCode.NotFound:
        Console.WriteLine("Resource not found");
        break;
    case HttpStatusCode.Unauthorized:
        Console.WriteLine("Authentication required");
        break;
    case HttpStatusCode.BadRequest:
        var error = await response.Content.ReadAsStringAsync();
        Console.WriteLine($"Bad request: {error}");
        break;
    default:
        Console.WriteLine($"Request failed with status: {response.StatusCode}");
        break;
}

Key Points to Remember

1. Use System.Text.Json: For .NET Core 3.0+, prefer System.Text.Json over Newtonsoft.Json for better performance
2. Proper Disposal: Always dispose of HttpClient using using statements or dependency injection
3. Content-Type: Set the correct content type header (e.g., application/json, application/x-www-form-urlencoded)
4. Error Handling: Always handle potential exceptions and check response status codes
5. Authentication: Add authorization headers when required by the API
6. Reuse HttpClient: Use IHttpClientFactory in production to avoid socket exhaustion

The PUT method is idempotent, meaning multiple identical requests should have the same effect as a single request. Use PUT when you want to update or replace an entire resource at a specific URL.