Web API Filters
| Filter Type | Interface | Class | Description |
| Authentication Filter | IAuthenticationFilter | - | Used to force users or clients to be aut ... |
| Authorization Filter | IAuthorizationFilter | AuthorizationFilterAttribute | Used to restrict access to action method ... |
| Exception Filter | IExceptionFilter | ExceptionFilterAttribute | Used to handle all unhandled exception i ... |
| Override Filter | IOverrideFilter | - | Used to customize the behaviour of other ... |
Full Answer
How to handle unhandled exceptions in web API using exception filter?
Exception filters can be used to handle unhandled exceptions which are generated in Web API. The exception filter can be able to catch the unhandled exceptions in Web API. This filter is executed when an action method throws the unhandled exception.
What is the difference between MVC and web API exception filter?
Exception filters in ASP.NET Web API are similar to those in ASP.NET MVC. However, they are declared in a separate namespace and function separately. In particular, the HandleErrorAttribute class used in MVC does not handle exceptions thrown by Web API controllers.
How to write an exception filter in ASP NET?
The simplest way to write an exception filter is to derive from the System.Web.Http.Filters.ExceptionFilterAttribute class and override the OnException method. Exception filters in ASP.NET Web API are similar to those in ASP.NET MVC. However, they are declared in a separate namespace and function separately.
What is the use of exceptionfilterresult in apicontroller?
When the ApiController (the base class for the Web API) executes an action from the class, it loads the ExceptionFilterResult if an exception occurs during the execution. The ExceptionFilterResult implements IHttpActionResult.
When to use exception filter?
We can use exception filter whenever controller action method throws an unhandled exception that is not an HttpResponseException. This is an attribute so we can decorate both action method and controller with this. Exception filter is very similar to HandleErrorAttribute in MVC.
What is the exception handling code?
Exceptions are the errors that happen at runtime. Exception handling is the technique to handle this runtime error in our application code. If any error is thrown in web API that is caught, it is translated into an HTTP response with status code 500- " Internal Server Error ".
What is Web API 2?
Web API 2 provides a good alternative way to achieve global exception handling. Web API provides " ExceptionHandler " abstract class to handle exception above said area.
What is the function of CreateErrorResponse?
CreateErrorResponse method of Request object helps us to return meaningful error code and message to the client. CreateErrorResponse creates an instance of HttpError object and returns it as HttpResponseMessage object.
When to use httpresponseException?
We can use HttpResponseException when the possibility of exception is known by us. In the above example, we have thrown exception using HttpResponseException class as we know there is a chance to employee not found in the database.
Do you need to register an exception handler?
Same as exception filter, Exception handler is also required to be registered. ExceptionHandler is inheriting from IExceptionHandler interface and Web API has already this type of class registered so we just need to replace this class to our custom exception handler class because Web API doesn’t support multiple ExceptionHandler.
What is a filter in web API?
Filters are actually attributes that can be applied on the Web API controller or one or more action methods. Every filter attribute class must implement IFilter interface included in System.Web.Http.Filters namespace. However, System.Web.Http.Filters includes other interfaces and classes that can be used to create filter for specific purpose.
What is a web API filter?
Web API includes filters to add extra logic before or after action method executes. Filters can be used to provide cross-cutting features such as logging, exception handling, performance measurement, authentication and authorization.
What is an interface in a filter?
Interfaces include methods that must be implemented in your custom attribute class whereas filter class has already implemented necessary interfaces and provides virtual methods, so that they can be overridden to add extra logic. For example, ActionFilterAttribute class includes methods that can be overridden. We just need to override methods which we are interested in, whereas if you use IActionFilter attribute than you must implement all the methods.
Can you create filters for cross-cutting concerns?
So now, it will log all the requests handled by above StudentController. Thus you can create filters for cross-cutting concerns.
Why do we need exception filters in NET Core?
This would ensure that application adheres to DRY principal. Once a filter is created, it can be applied to as many controllers or action as the application needs. Also, as this is the single place to handle exception, appropriate code can be added to avoid leaking stack traces to callers.
What is exception handling?
Exceptions and Exception handling is one important aspect of application development, application monitoring. In this application, let’s try to understand different ways to handle exceptions in an ASP .NET Core Web API application.
Why choose middleware over filters ?
Invoking middleware happens way before deciding a controller and an action which can handle the incoming request.
What is exception handling middleware?
The exception handling middleware is invoked for all the controllers in an application. Invoking middleware happens way before deciding a controller and an action which can handle the incoming request. On the other hand, filters invoked after request has gone through routing middleware. So, the controller and the action to be executed is known.
What happens when you use multiple catch blocks?
If multiple catch blocks are used, then the exception types used in the catch block should be ordered in such a way that catch blocks for more specific exception type should appear before catch blocks for more general types to ensure that right catch block is matched.
What is UseExceptionMiddleware?
UseExceptionMiddleware takes a URL as parameter, where a route can be specified. This route would be invoked to handle the error and return appropriate response to the caller.
Is ExceptionFilterAttribute useful in NET?
Although an extended ExceptionFilterAttribute might seem to be helpful in solving original issues mentioned in first approach (i. e. try-catch blocks), .NET documentation recommends newer way. And it is to use exception handling middleware UseExceptionHandler in .NET’s request processing pipeline.
What is exception filter?
Normally, exception filter is used to catch the unhandled exception. This approach will work fine but it fails if any error is raised from outside action. For example, if any error is raised in the following area then exception filter will not work.
Why does the exception filter not catc h HttpResponseException?
Note that exception filter does not catc h HttpResponseException exception because HttpResponseException is specifically designed to return the HTTP response.
What happens if a Web API controller throws an uncaught exception?
What happens if a Web API controller throws an uncaught exception? By default, most exceptions are translated into an HTTP response with status code 500, Internal Server Error.
What is a CreateErrorResponse?
CreateErrorResponse is an extension method defined in the System.Net.Http .HttpRequestMessageExtensions class. Internally, CreateErrorResponse creates an HttpError instance and then creates an HttpResponseMessage that contains the HttpError.
What is an ExceptionFilterResult?
When the ApiController (the base class for the Web API) executes an action from the class, it loads the ExceptionFilterResult if an exception occurs during the execution. The ExceptionFilterResult implements IHttpActionResult. The ExceptionFilterResult catches all exception and then passes these exceptions to the Exception Filter attribute. We have the liberty to implement the Exception filter as per the logical requirements of our application.
What is the benefit of using ASP.NET Web API?
A benefit of using ASP.NET Web API is that it can be consumed by any client with the capability of making HTTP calls and processing JSON data. The client can use HTTP methods to perform Read/Write operations. They make use of HttpRequestMessage and HttpResponseMessage to manage messaging to and from Web API.
What is an exception filter?
Using exception filters is a good technique of centralizing the handling of an exception. The only limitation of this approach is that it’s effective for only the API pipeline. If there is an exception in other layers of your app apart from the API layer then this approach won’t be helpful. Example – It won’t catch the exception ...
Why are filters important?
Filter helps in abstracting your repetitive and important cross-cutting concerns and make your business logic free of addressing those concerns repeatedly .
