Constant Expressions
A constant expression consists of a constant value. Constant values are directly converted to constant command tree expressions, without any translation on the client. This includes expressions that result in a constant value. Therefore, data source behavior should be expected for all expressions involving constants. This can result in behavior that differs from CLR behavior.
The following example shows a constant expression that is evaluated on the server.
Using AWEntities As New AdventureWorksEntities()
Dim sales As ObjectQuery(Of SalesOrderHeader) = AWEntities.SalesOrderHeader
Dim salesInfo = _
From s In sales _
Where s.TotalDue >= 200 + 3 _
Select s.SalesOrderNumber
Console.WriteLine("Sales order numbers:")
For Each orderNum As String In salesInfo
Console.WriteLine(orderNum)
Next
End Using
using (AdventureWorksEntities AWEntities = new AdventureWorksEntities())
{
ObjectQuery<SalesOrderHeader> sales = AWEntities.SalesOrderHeader;
IQueryable<string> salesInfo =
from s in sales
where s.TotalDue >= 200 + 3
select s.SalesOrderNumber;
Console.WriteLine("Sales order numbers:");
foreach (string orderNum in salesInfo)
{
Console.WriteLine(orderNum);
}
}
LINQ to Entities does not support using a user class as a constant. However, a property reference on a user class is considered a constant, and will be converted to a command tree constant expression and executed on the data source.