Uniform, consistent error responses from ASP.Net Web API 2

Question

I\'m developing a Web API 2 application and I\'m currently trying to format error resposnes in a uniform way (so that the consumer will also know what data object/structure

Answer 1

I have done in same way as @Dan H mentioned

 public class ApiGatewayHandler : DelegatingHandler
{
    protected async override Task SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        try
        {
            var response = await base.SendAsync(request, cancellationToken);
            if (response.StatusCode == HttpStatusCode.NotFound)
            {
                var objectContent = response.Content as ObjectContent;
                return await Task.FromResult(new ApiResult(HttpStatusCode.NotFound, VmsStatusCodes.RouteNotFound, "", objectContent == null ? null : objectContent.Value).Response());
            }
            return response;
        }
        catch (System.Exception ex)
        {
            return await Task.FromResult(new ApiResult(HttpStatusCode.BadRequest, VmsStatusCodes.UnHandledError, ex.Message, "").Response());
        }

    }
}

Added routing like below and now it hits the try catch for invalid url

  config.Routes.MapHttpRoute(name: "DefaultApi",routeTemplate: "api/{controller}/{id}",defaults: new { id = RouteParameter.Optional });
        config.Routes.MapHttpRoute(name: "NotFound", routeTemplate: "api/{*paths}", defaults: new { controller = "ApiError", action = "NotFound" });