>>I agree that it sounds as if you are referencing the correct class/assembly in web.config.
>>But I don't know why the redirect didn't work (or, come to that, why the default validator was called)
>>The implication is that although properly referenced your class is not in fact being used.
>>Are you sure the page in question is within the relevant web.config scope?
>>Is your IsValidRequestString method calling the base class implementation ?
>>First step is to establish for sure whether your method is being called (either via debug or event logging?)
>>FWIW I just tested using the sample class I posted earlier and that worked as expected so the principle is correct.....
>
>When I change the Web.Config, I can see that it takes a little bit longer for that link, the one I use for testing, to come up. So, this is an indication that it uses the right Web.Config file.

It might be an indication that it is being compiled/loaded. That doesn't mean it will be used. You really need to get positve proof that the method is being called.

>As for calling the base class implementation, isn't the inherit the line for that?

Since you override the IsValidRequestString you must call the base implementation if you also want to use the default behaviour:

Return MyBase.IsValidRequestString(context, value, requestValidationSource__1, collectionKey, validationFailureIndex)

But, of course, you only need use the default validation if you want it.....

>The only think I could think of is that is being run locally. So, my URL is something like http://localhost/LevelExtreme20/&.
Don't see why that should be a problem. I tested here using local dev server.

>Another think I could think of is that the main dll to run the Web site is LevelExtreme.dll and Framework.dll is referenced in it.
Again, shouldn't be a factor.....