实体框架错误，试图获取Linq到实体的行数

Question

When I try to run this code:

var qry = ( from v in db.Visits
           where v.VisitorID == visitorID
              && v.IncomingID == incomingID
              && v.ProjectID == ProjectID.GetID()
           select v.VisitorID);

int visits = qry.Count();

The qry runs okay but the "int visits = ..." line bombs out with "LINQ to Entities does not recognize the method 'Int32 GetID()' method, and this method cannot be translated into a store expression."

What am I doing wrong?

Answer 1

what you are doing wrong, is that ProjectID.GetID() can not be called in linq to entity, you can call this before your query:

var o = ProjectID.GetID();
var qry = (from v in db.Visits
           where v.VisitorID == visitorID && 
                 v.IncomingID == incomingID && 
                 v.ProjectID == o 
           select v.VisitorID);

int visits = qry.Count();

Answer 2

You can't call custom methods in a query like this.

LINQ to Entities works by building an expression tree in order to convert to a database query. It sees ProjectID.GetID() and it has no idea how to translate that into SQL.