无法使用MVC 4 beta修改表中的记录但我可以添加记录

I am new to MVC framework. I am using MVC 4 beta and now I am having some trouble. I have googled alot but could not found a solution to my problem so here I am hoping that some one can help with that. My problem is I have two databasesI am new to MVC framework. I am using MVC 4 bet