Exception Handling In ASP.NET Web API

Jignesh Trivedi

5y664.1k22100Article

22 Comments

Join the conversation! Your thoughts help the community grow.

md ameen5y ago
Nice Article
Abirami Senthil6y ago
For using Exception handler how the end point implementation will look like
- Jignesh Trivedi6y ago
  I am not sure I understand your question correctly but it has no end point, it just return response in case of exception
Hoang Minh6y ago
Hi guys, I have a Web API is running e.g: http://localhost:52237. It works as well while I call api e.g: http://localhost:52237/api/payment/registerpayment by http POST via postman tool with request and body. Then I've created a Web application. How can I capture any http request & response as well as postman tool?
Chittaranjan Swain6y ago
Nice article....
Vittorio Morellini7y ago
Hello, the handler has to an ashx ?
- Jignesh Trivedi7y ago
  You can use try catch block or you can add Application_Error block in global.asax to handle exception
Akshay Dalvi7y ago
Appreciate your efforts. Thanks!
Prem Kumar7y ago
Worth reading. Great job Jignesh!
nitesh poddar7y ago
Very good sir :)
Sachith Wickramaarachchi8y ago
Good article, thanks for share
Sudhir Rao8y ago
Very good article for getting started on the subject
amit khajuria8y ago
Very nice Article, easy to understand
rupinder batra9y ago
Nice Article...easy to understand.
Kuppurasu Nagaraj10y ago
Nice Sharing..
Sonu Chaudhary10y ago
good one...
Bhavik Patel10y ago
nice
Ketak Bhalsing10y ago
Helpful information....
Nitin10y ago
Good work
Thiruppathi R10y ago
Very Nice ...
Debasis Saha10y ago
Nice one..
Akshay Phadke10y ago
Nice article buddy you should write more often :)

Introduction

In this article, we will define exception handling in the ASP.NET Web API.

Excepting handling is a process that handles an exception by saving the current state of execution and switches the execution to the specific subroutine. The following are used:

HttpResponseException
Exception Filter
Registering Exception Filters
HttpError

HttpResponseException

It is a special type of exception. It throws an HTTP code as an exception that is defined in the exception constructor. In it the exception is converted into a HTTP response.

public Detail GetDetail(int Id)
{
Detail item = reposite.Get(Id);
if (val == null)
{
throw new HttpResponseException(HttpStatusCode.NotFound);
}
return val;
}

If there is an Id parameter not defined then it will return the response "NotFound".

We can create own response message for controlling the resoponse, and this message wille be included with the HttpResponseException.

public Detail GetDetail(int Id)
{
Detail val = reposite.Get(Id);
if (item == null)
{
var show = new HttpResponseMessage(HttpStatusCode.NotFound)
{
Con = new StringContent(string.Format("There is no Detail with Id {0}", Id)),
Reason_Phrase = "Detail Id not defined"
}
throw new HttpResponseException(Show);
}
return val;
}

Exception Filters:

If there is any Unhandled type exception generated that is not the HttpResponseException type Exception then the Exception filter is used to handle these exceptions. It is written using the Web API.

The "System.Web.Http.Filters.IExceptionFilter" interface and "System.Web.Http.ExceptionFilterAttribute" class are used.

namespace hello.Filters
{
using System;
using System.Net;
using System.Net.Http;
using System.Web.Http.Filters;
public class E_Filter : ExceptionFilterAttribute
{
public override void OnException(HttpActionExecutedContext cont)
{
if (cont.Exception is NotImplementedException)
{
cont.Response = new HttpResponseMessage(HttpStatusCode.NotImplemented);
}
}
}
}

Registering Exception Filters

We register the exception in various ways that are as follows:

Globally
By Action
By Controller

Globally

When the exception is registered globally, first we need to create an instance of the GlobalConfiguration.Configuration.Filters.

GlobalConfiguration.Configuration.Filters.Add(new hello.E_Filter());

If we are working on ASP.NET MVC 4 Application then we add the API configuration code in WebApiConfig.cs class that is located in the App_Start folder.

public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
config.Filters.Add(new hello.E_Filter());
}
}

By Action:

We can also apply a filter for the specific action.

public class DetailController : ApiController
{
[NotImplExceptionFilter]
public contact GetContact(int id)
{
throw new NotImplementedException("method can not be implement");
}
}

By Controller

We can apply the filter on the all method of a controller.

[NotImplExceptionFilter]
public class DetailController : ApiController
{
}

HttpError

HttpError provides a way to show the error message.

public class DetailController : ApiController
{
public HttpResponseMessage GetDetail(int Id)
{
Detail val = reposite.Get(Id);
if (val == null)
{
var report = string.Format("Id of Detail = {0} ",Id);
HttpError error = new HttpError(report);
return Request.CreateResponse(HttpStatusCode.NotFound, error);
}
else
{
return Request.CreateResponse(HttpStatusCode.OK, val);
}
}
}

We can also use the CreateErrorResponse instead of HttpError.

Let's see an example of CreateErrorResponse:

public class DetailController : ApiController
{
public HttpResponseMessage GetDetail(int Id)
{
Detail val = reposite.Get(Id);
if (val == null)
{
var report = string.Format("Id of Detail = {0} ",Id);
return Request.CreateErrorResponse(HttpStatusCode.NotFound, error);
}
else
{
return Request.CreateResponse(HttpStatusCode.OK, val);
}
}
}

This is the description of exception handling.