How to do DataAnnotation in database first approach

Hi ,

 you can add a metadata class that contains the attributes. When you associate the model class to the metadata class, those attributes are applied to the model. In this approach, the model class can be regenerated without losing all of the attributes that have been applied to the metadata class.

 check this 

 http://www.asp.net/mvc/overview/getting-started/database-first-development/enhancing-data-validation