manipulación DateTime dentro de LINQ to Entities

Question

la ejecución de este código:

public bool CheckTime(DateTime date, int UserID, int TotalTimeMin) 
     { 
      using (var context = new myDB()) 
      {   
       var assginments = from c in context.Assignments.Where(x=>(x.AssignmentDateTime < date && x.AssignmentDateTime.Value.AddMinutes(TotalTimeMin) > date) || 
        (x.AssignmentDateTime < date.AddMinutes(TotalTimeMin))) select c; 

       if(assginments != null) return false; 
       else return true; 
      } 


     } 

consigo este error.

LINQ to Entities does not recognize the method 'System.DateTime AddMinutes(Double)' method, and this method cannot be translated into a store expression. 

TotalTimeMin es int. No estoy seguro de por qué: AssignmentDateTime is DateTime? y tal vez este es el problema?

Answer 1

Uso EntityFunctions.AddMinutes (requiere EF 4):

public bool CheckTime(DateTime date, int UserID, int TotalTimeMin) 
    { 
     using (var context = new myDB()) 
     {   
      var assginments = context.Assignments 
            .Where(x=>(x.AssignmentDateTime < date 
               && EntityFunctions.AddMinutes(x.AssignmentDateTime,TotalTimeMin) > date) 
               || (x.AssignmentDateTime < date.AddMinutes(TotalTimeMin))); 

      if(assginments != null) return false; 
      else return true; 
     } 
    } 

Tenga en cuenta que nunca se assignments se ser nulo (pero podría estar vacío - prueba assignments.Any()).