EntityServerSaveInterceptor - How

   I need to override the EntityServerSaveInterceptor. I don't understand where to do this. I have three projects:
Business Logic - Provides data from the Entity Model to the WebService
EntityModel - contains only entities
WebService - web service that using the Business Logic project to provide data

When I create the entity manager I set this property  this.VerifierEngine.DefaultVerifierOptions.ShouldTreatEmptyStringAsNull = false. This does not work for the server validation so I created the class below to do this.
Which project do I put this class in and how do I override the server code ?
 public class mnstSaveInterceptor : EntityServerSaveInterceptor  
    {
        protected override bool ValidateSave() {
            this.VerifierEngine.DefaultVerifierOptions.ShouldTreatEmptyStringAsNull = false;
            return base.ValidateSave();
        }
    }
TIA Bill