Practical .NET

Send the Right Error Information with HttpException

When something goes wrong with your Web Service the decent thing to do is to return your errors in a variety of ways.

One way to return an error from a Web Service is to raise an HttpException. If you do so, you should support two methods and one property on the HttpException object:

  • GetHttpCode: One of the HTTP protocol's predefined codes
  • GetHtmlMessage: An HTML-formatted message suitable for display in a Web page
  • Message: A plain text string containing useful information about the error

Probably the easiest way to do this is to pass the exception that your service ran into as the third parameter when creating the HttpException object. The odds are good that the ErrorFormatter that generates the HttpException object's HTML will be able to convert your exception into HTML.

Your resulting code would look like this (using 500, the standard HTTP code for "something has gone horribly wrong on the server"):

Try
  '...code with potential problem...
Catch (ex As Exception)
  Throw New Exception(500, "Something has gone horribly wrong", ex)
End Try

Now, that's a strong message no one can ignore.

About the Author

Peter Vogel is a system architect and principal in PH&V Information Services. PH&V provides full-stack consulting from UX design through object modeling to database design. Peter tweets about his VSM columns with the hashtag #vogelarticles. His blog posts on user experience design can be found at http://blog.learningtree.com/tag/ui/.

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