System.Web.Http.HttpResponseException – Response status code does not indicate success

The System.Web.Http.HttpResponseException with the message “Response status code does not indicate success” is an exception thrown in ASP.NET Web API applications when an HTTP request returns a non-success status code (e.g., 4xx or 5xx). This exception is commonly encountered when making HTTP requests using HttpClient or during API controller actions.

---

Key Points

• This exception is specific to ASP.NET Web API and HttpClient.
• It indicates that the HTTP response status code is not in the 2xx range (e.g., 200 OK).
• Common causes include invalid requests, server errors, or issues with the API endpoint.

---

Common Causes

1. Client-Side Issues:

• Invalid request parameters (e.g., missing or incorrect data).
• Incorrect HTTP method (e.g., using POST instead of PUT).
• Unauthorized access (e.g., missing or invalid authentication tokens).

1. Server-Side Issues:

• The API endpoint returns a non-success status code (e.g., 400 Bad Request, 404 Not Found, 500 Internal Server Error).
• The server encounters an error while processing the request.

1. Network Issues:

• Connectivity problems or timeouts when making the request.

1. Misconfigured HttpClient:

• Incorrect base address, headers, or request configuration.

---

How to Fix

Client-Side Fixes

1. Check Request Details:

• Verify the URL, HTTP method, headers, and request body.
• Ensure the request is correctly formatted and includes all required data.

1. Handle Non-Success Status Codes:

• Use HttpResponseMessage.EnsureSuccessStatusCode() to throw an exception for non-success status codes, and handle it gracefully.

   try
   {
       HttpResponseMessage response = await httpClient.GetAsync("api/data");
       response.EnsureSuccessStatusCode(); // Throws HttpResponseException if status code is not successful
       string responseData = await response.Content.ReadAsStringAsync();
   }
   catch (HttpResponseException ex)
   {
       Console.WriteLine($"Error: {ex.Response.StatusCode} - {ex.Response.ReasonPhrase}");
   }

3. Validate Input:

• Ensure the request data is valid before sending it to the server.

3. Check Authentication:

• Verify that the request includes valid authentication tokens or credentials.

---

Server-Side Fixes

1. Return Meaningful Error Responses:

• Ensure the API returns detailed error messages and appropriate status codes.

   public IHttpActionResult GetData(int id)
   {
       var data = repository.GetData(id);
       if (data == null)
       {
           return NotFound(); // Returns 404 Not Found
       }
       return Ok(data); // Returns 200 OK
   }

2. Log Errors:

• Log server-side errors for debugging and monitoring.

   catch (Exception ex)
   {
       logger.LogError(ex, "An error occurred while processing the request.");
       return InternalServerError(); // Returns 500 Internal Server Error
   }

3. Validate Requests:

• Use model validation to ensure the request data is valid.

   if (!ModelState.IsValid)
   {
       return BadRequest(ModelState); // Returns 400 Bad Request
   }

---

Example Scenario

Client Request

using (HttpClient httpClient = new HttpClient())
{
    httpClient.BaseAddress = new Uri("https://api.example.com");
    HttpResponseMessage response = await httpClient.GetAsync("api/data/123");
    response.EnsureSuccessStatusCode(); // Throws HttpResponseException if status code is not successful
    string responseData = await response.Content.ReadAsStringAsync();
}

Server Response (404 Not Found)

HTTP/1.1 404 Not Found
Content-Type: application/json

{
  "error": "Not Found",
  "message": "The requested resource was not found."
}

---

Debugging Tips

1. Inspect Response:

• Check the response status code and body for details about the error.

   HttpResponseMessage response = await httpClient.GetAsync("api/data");
   Console.WriteLine($"Status Code: {response.StatusCode}");
   Console.WriteLine($"Response Body: {await response.Content.ReadAsStringAsync()}");

2. Use Tools:

• Use tools like Postman, Fiddler, or browser developer tools to inspect the request and response.

2. Check Logs:

• Review server logs to identify the root cause of the error.

---