From your stack trace and the innerException I can see that you're trying to serialize a KeyValuePair<string, string> and I guess this comes from a dictionary<string, string> but the XML serializer can't
save IDictionary objects:
Q: Why can't I serialize hashtables?
A: The XmlSerializer cannot process classes implementing the IDictionary interface. This was partly due to schedule constraints and partly due to the fact that a hashtable does not have a counterpart in the XSD type system. The only solution is to implement a custom hashtable that does not implement the IDictionary interface.
Instead of saving dictionary<string, string> you could try to convert it to List<MyObject> where MyObject is:
(note: the default constructor is important so that the Activator could create an instance of this class)
I hope I was able to help you and if you have further questions please feel free to ask.
All the best,
the Telerik team