validation error

it is not possible for me to use validation ,asction and behavior option.when i click on them ,this error is shown:

Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.


Dear Pooneh

In order to better assist you please send us further information about the task your want to accomplish, the way you are using the tools, and the complete error message you obtain. send some screenshot will be useful to better understand you issue.

best regards

Luis Emilio