c# - Entity Framework: Unable to create a constant value of type **. Only primitive types or enumeration types are supported in this context -

i have query:

     public override ienumerable<order> executequery(movierentalcontext database)     {          return order in database.orders             (customer == null || customer.id == order.customerid)             select order;     } 

where customer field in class. there order class

   public class order: entity {     [required]     public copy copy { get; set; }      public customer customer { get; set; }     public datetime orderdate { get; set; }     public datetime estimatedreturndate { get; set; }     public salesman salesman { get; set; }      public datetime? actualreturndate { get; set; }     public decimal price { get; set; }      [foreignkey("customer")]     public long customerid { get; set; } } 

entity contains id. want orders of customer, during execution query exception thrown:

unable create constant value of type >'movierental.dataaccess.models.customer'. primitive types or enumeration >types supported in context.

i tried found stil doesn't work. problem?

i'd customer == null code causing this. ef trying convert sql customer not in context. try , take condition outside of query.

ie

public override ienumerable<order> executequery(movierentalcontext database) {     if (customer != null)     {         return order in database.orders             order.customerid == customer.id             select order;     }     else     {         return order in database.orders             select order;     }  }