LINQ To Entities Does Not Recognize The Method [Type] GetValue[Type]?

I've a simple class like this:

Public Class CalculationParameter{
public Long TariffId{get;set;}
}

In a workflow activity, I've an Assign like this:

(From tariffDetail In db.Context.TariffDetails
Where tariffDetial.TariffId = calculationParameter.TariffId).FirstOrDefault()

Dto is passed to Activity as an Input Argument.It raise following error and I'm wondering how to assign Id.LINQ to Entities does not recognize the method 'Int64

GetValue[Int64](System.Activities.LocationReference)' method, and this method cannot be translated into a store expression.

How can I assign the calculationParameter.TariffId to tariffDetial.TariffId?!

UPDATE:Screen shot attached shows that how I'm trying to assign calculationParameter.TariffId to tariffDetail.TariffId (car.Id = Dto.Id) and the query result should assign to CurrentTrafficDetail object.