how to retrieve actual error message in case of Bad Request using OwinContext middleware in .Net Web Api 2?

Question

When .Net web API returns Badrequest("this is an example of Badrequest".), IOwinContext object in my middleware only contains context.Response.StatusCode 400 and context.Response.ReasonPhrase as "Bad Request". I want actual error message so that I can log it somewhere. Is it possible to get actual error message from IOwinContext without writing any custom class?

EDIT: Startup.cs

public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            ICoreLogger dv_logger = new CoreLogger();
            app.Use<InvalidAuthenticationMiddleware>(dv_logger);
            ConfigureOAuth(app);
            //register log4net
            XmlConfigurator.Configure();
            // configure log4net variables
            GlobalContext.Properties["processId"] = "dv_logger";
            System.Web.Http.GlobalConfiguration.Configure(WebApiConfig.Register);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            //entity framework
            DbContext.Intialize();
            AuthContext.Intialize();
            .....
   }

Middleware

 public class InvalidAuthenticationMiddleware : OwinMiddleware
{
        public override async Task Invoke(IOwinContext context)
        {
            var stream = context.Response.Body;
            using (var buffer = new MemoryStream())
            {
                context.Response.Body = buffer;
                await Next.Invoke(context);

                buffer.Seek(0, SeekOrigin.Begin);
                using (var reader = new StreamReader(buffer))
                {
                    string responseBody = await reader.ReadToEndAsync();

                    if (context.Response.StatusCode == (int)HttpStatusCode.BadRequest)
                    {
                        var definition = new { Message = "" };
                        var error = JsonConvert.DeserializeAnonymousType(responseBody, definition);

                        Debug.WriteLine(error.Message);
                    }

                    buffer.Seek(0, SeekOrigin.Begin);
                    await buffer.CopyToAsync(stream);
                }
            }
        }

}

Controller

public class LoginController : BaseController
{
        [Route("")]
        public IHttpActionResult Get(string email)
        {
           return BadRequest("this is an example of bad request!");
        }
}

What does `ConfigureOAuth()` do? Why aren't you using `appBuilder.UseWebApi(config)` instead of `GlobalConfiguration.Configure()`? You should simplify your `Startup.Configuration()` and remove some parts to narrow down your problem. — Anouar, Jun 04 '20 at 09:36
We were using ```appBuilder.UseWebApi(config)``` but we also have a MVC controller in our project. So, we had to switch to ```GlobalConfiguration.Configure()```. ```ConfigureOAuth``` sets property for Owin Authorization. — shrey shah, Jun 22 '20 at 14:31

score 0 · Answer 1 · answered Jun 03 '20 at 12:41

0

You will have to read the response's body. BadRequest("this is an example of BadRequest") sets an object in the body of the response with a property Message containing that message. I am assuming you are using JSON as a serialization format:

{
    "Message": "this is an example of BadRequest"
}

Here is the middleware code to log the error message when the response is a BadRequest:

public override async Task Invoke(IOwinContext context)
{
    var stream = context.Response.Body;
    using (var buffer = new MemoryStream())
    {
        context.Response.Body = buffer;

        await next.Invoke();

        buffer.Seek(0, SeekOrigin.Begin);
        using (var reader = new StreamReader(buffer))
        {
            string responseBody = await reader.ReadToEndAsync();

            if (context.Response.StatusCode == (int)HttpStatusCode.BadRequest)
            {
                var definition = new { Message = "" };
                var error = JsonConvert.DeserializeAnonymousType(responseBody, definition);

                Console.WriteLine(error.Message);
            }

            buffer.Seek(0, SeekOrigin.Begin);
            await buffer.CopyToAsync(stream);
        }
    }
}

Note that I used an anonymous type to avoid having to declare a class for the error message object.

answered Jun 03 '20 at 12:41

Anouar

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responseBody variable always sets to an empty string if I run above code. Any suggestion? – shrey shah Jun 03 '20 at 14:08
How do you register your middleware? Can you include a minimal sample of your code (your controller returning the BadRequest + your startup)? – Anouar Jun 03 '20 at 14:15
app.Use(dv_logger); here, InvalidAuthenticationMiddleware contains your code. Controller: return BadRequest("this is an example of bad request!"); – shrey shah Jun 03 '20 at 14:51
Don't you have a `app.UseWebApi(config);` also? The order in which you register middlewares is important. Make sure you register your `InvalidAuthenticationMiddleware` before `app.UseWebApi(config);`. In general, the logging middleware has to be registered first. – Anouar Jun 03 '20 at 15:12
yes. middleware is registered before ```System.Web.Http.GlobalConfiguration.Configure(WebApiConfig.Register);``` – shrey shah Jun 03 '20 at 15:17
I would highly recommend that you update your question to add your example code. Otherwise it would be impossible for me or anyone else to help find your problem cause. – Anouar Jun 03 '20 at 15:22
added example code in the question. please look at it. – shrey shah Jun 04 '20 at 05:38

how to retrieve actual error message in case of Bad Request using OwinContext middleware in .Net Web Api 2?

1 Answers1