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Add an Error Handler to Your ASP.NET MVC Controller

There really isn't such a thing as an "unhandled error" -- if your code throws an error outside of a Try...Catch block, then your error bubbles up through various ASP.NET and .NET Framework error handlers. An "unhandled error" is just an error that you aren't handling.

In ASP.NET MVC you can handle more errors by inserting an error handler inside your Controller: Just add an OnException method to your Controller. The code in this method will be invoked each time you have an "unhandled error" in that Controller.

It's easy to add the method: In your Controller, just type Overrides (in Visual Basic) or override (in C#), press the Tab key to get a list of overrideable methods, pick OnException from the list, and press the Tab key again. Visual Studio will write out the skeleton of the method for you.

The Visual Basic version looks like this:

Protected Overrides Sub OnException(filterContext As ExceptionContext)

End Sub

Your method will be passed an ExceptionContext object whose Exception property will give you access to all of the information about what went wrong. Within your OnException method you can do whatever you want about the error that's specific to the Controller (log to some audit file, for example). If you take no further action, the error will continue to bubble up to the ASP.NET error handler.

If, however, you wanted to finish by using the RedirectToRouteResult method built into your Controller to send the user the error page of your choice then you need to stop that bubbling process. You can do with this line:

filterContext.ExceptionHandled = True

which sets the ExceptionContext object's ExceptionHandled property to True.

Posted by Peter Vogel on 08/09/2016 at 9:53 AM


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