Parser Error: Server Error in '/' Application

Question

I got the following error: \"An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details a

Answer 1

This happened to me when i was trying to merge two solutions. the problem was the namespace was not well configured in all files. one part of story solved with @Kevin Aenmey answer but many other's ... not!

so the only way for me was to search for old namespace in the whole solution and replace them all with new namespace.maybe not the best option but in case of bad luck works nice