Error handling (Sending ex.Message to the client)

Question

I have an ASP.NET Core 1.0 Web API application and trying to figure out how to pass the exception message to the client if a function that my controller is calling errors out.

I have tried so many things, but nothing implements IActionResult.

I don't understand why this isn't a common thing that people need. If there truthfully is no solution can someone tell me why?

I do see some documentation out there using HttpResponseException(HttpResponseMessage), but in order to use this, I have to install the compat shim. Is there a new way of doing these things in Core 1.0?

Here is something I have been trying with the shim but it isn't working:

// GET: api/customers/{id} [HttpGet("{id}", Name = "GetCustomer")] public IActionResult GetById(int id) {     Customer c = _customersService.GetCustomerById(id);     if (c == null)     {         var response = new HttpResponseMessage(HttpStatusCode.NotFound)         {             Content = new StringContent("Customer doesn't exist", System.Text.Encoding.UTF8, "text/plain"),             StatusCode = HttpStatusCode.NotFound          };          throw new HttpResponseException(response);          //return NotFound();     }     return new ObjectResult(c); } 

When the HttpResponseException is thrown, I look on the client and can't find the message I am sending anything in the content.

Answer 1

Here is an simple error DTO class

public class ErrorDto {     public int Code {get;set;}     public string Message { get; set; }      // other fields      public override string ToString()     {         return JsonConvert.SerializeObject(this);     } } 

And then using the ExceptionHandler middleware:

            app.UseExceptionHandler(errorApp =>             {                 errorApp.Run(async context =>                 {                     context.Response.StatusCode = 500; // or another Status accordingly to Exception Type                     context.Response.ContentType = "application/json";                      var error = context.Features.Get<IExceptionHandlerFeature>();                     if (error != null)                     {                         var ex = error.Error;                          await context.Response.WriteAsync(new ErrorDto()                         {                             Code = <your custom code based on Exception Type>,                             Message = ex.Message // or your custom message                             // other custom data                         }.ToString(), Encoding.UTF8);                     }                 });             }); 

Answer 2

Yes it is possible to change the status code to whatever you need:

In your CustomExceptionFilterAttribute.cs file modify the code as follows:

public class CustomExceptionFilterAttribute : ExceptionFilterAttribute {     public override void OnException(ExceptionContext context)     {         var exception = context.Exception;         context.Result = new ContentResult         {             Content = $"Error: {exception.Message}",             ContentType = "text/plain",             // change to whatever status code you want to send out             StatusCode = (int?)HttpStatusCode.BadRequest          };     } } 

That's pretty much it.

If you have custom exceptions, then you can also check for them when grabbing the thrown exception from the context. Following on from that you can then send out different HTTP Status Codes depdending on what has happened in your code.

Hope that helps.