Created Unassigned: WebApi model binding fails when Property inherits from Dictionary [1087]

When I submit the webpage data to the ApiController the binding will not bind the MyDictionary<string, string> ExtraData property. If I change the property to Dictionary<string, string> ExtraData property then Api controller will bind correctly. However this is not an option because the MyDictionary class has additional functionality that I need. I have four buttons on the webpage for submitting data to the apicontroller. The red button fails to load the MyDictionary ExtraData property. The 3 green buttons load MyDictionary and Dictionary property ok.