ELMAH filtering of exceptions by type using the is-type assertion

PROBLEM: In one of our projects, validation errors are thrown as exceptions (ValidationException) - we obviously don't want to be notified about a user forgetting a mandatory field etc, and luckily ELMAH has support to filter out certain exceptions from being logged and/or emailed.  Have a read here: https://code.google.com/p/elmah/wiki/ErrorFiltering and here https://code.google.com/p/elmah/wiki/ErrorFilterExamples and here http://www.diaryofaninja.com/blog/2011/09/20/adding-filters-to-your-elmah-installation

I tried the following in the web.config and it resulted in a runtime error:

<errorFilter>
  <test>
    <is-type binding="BaseException" type="MyProject.Models.ValidationException" />
  </test>
</errorFilter>

SOLUTION:
You need to include the assembly name e.g.

<errorFilter>
  <test>
    <is-type binding="BaseException" type="MyProject.Models.ValidationException, MyProject" />
  </test>
</errorFilter>

(this isn't in the limited doco of ELMAH but the creator of ELMAH does mention it in a random forum post i.e. "In the type attribute of the is-type element, you forgot to specify the assembly where the CustomLibrary.CustomException type can be found. In absence of the assembly specification, ELMAH looks for the type in its own assembly. If your assembly name is the same as the namespace (i.e. CustomLibrary) then try changing the is-type element to read as follows: <is-type binding="Exception" type="CustomLibrary.CustomException, CustomLibrary" />"