Best API error exception practise with generated REST API code

Radzen Blazor Studio
1

I used the REST API generator to create an API service to call a REST API (my own). It nicely generated the code below.

        public async Task<MyApp.Models.MyAppApi.PostMeasureCalculate> PostCalculate(Models.MyAppDevDb.EMeasure eCMeasure)
        {
            var uri = new Uri(httpClient.BaseAddress, $"measure/calculate");

            var request = new HttpRequestMessage(HttpMethod.Post, uri);
            
            request.Content = JsonContent.Create<Models.MyAppDevDb.EMeasure>(eMeasure);

            OnPostMeasureCalculate(request);

            var response = await httpClient.SendAsync(request);

            // My aim is to use custom code here to extract error details from response.Content before throwing the exception
            response.EnsureSuccessStatusCode(); // Throws an exception that only contains: "Response status code does not indicate success: 400 (Bad Request)."

            OnPostMeasureCalculateResponse(response);

            return await response.Content.ReadFromJsonAsync<MyApp.Models.MyAppApi.PostMeasureCalculate>();
        }

Problem: before I am able to get more details out of the response about any error, the call response.EnsureSuccessStatusCode() throws an exception and the response.content data is lost.
The only information left, if I catch the thrown exception in my *.razor.cs UI code is:

Response status code does not indicate success: 400 (Bad Request).

But my response.content would have been "Parameter x,y,z was invalid."

Question: How to process response.content in an error case, without changing "generated" code. I would like to do it over the callbacks that are provided by Radzen.
Thank you for any hints.

2

Hi,

There isn’t any built in way to process the error response without modifying the generated code.

3

Thank you @korchev for your quick feedback. That helps me to determine how to go on.
To keep the generated code as clean as possible I decided to comment
// response.EnsureSuccessStatusCode(); in it.

And implement the OnPostMeasureCalculate(response) function which is called right after the commented line in custom file MyAppApiService.Custom.cs.
It will get further error details from my response and add it to the thrown exception.

        partial void OnPostMeasureCalculate(HttpResponseMessage response)
        {
            DetectHttpResponseError(response);
        }

        void DetectHttpResponseError(HttpResponseMessage response)
        {
            if (response.IsSuccessStatusCode)
            {
                return;
            }
            string errorContent = "";
            if (response.Content != null)
            {
                // The HTTP request failed, let's see if we have additional error information
                errorContent = response.Content.ReadAsStringAsync().Result;
                ErrorResponse errorResponse = null;

                // The HTTP request failed, let's see if we have additional error information                
                try
                {
                    errorResponse = JsonConvert.DeserializeObject<ErrorResponse>(errorContent);
                    Console.WriteLine($"Request failed with status code: {response.StatusCode}");
                    Console.WriteLine($"Error message: {errorResponse.Message}");
                    throw new HttpRequestException(errorResponse.Message);
                }
                catch (JsonReaderException)
                {
                    // When the JSON interpretation failed, we just stick with the original error content
                }
            }
            throw new HttpRequestException(errorContent);
        }

Hope that helps somebody else too. Happy to read from any other approachs.