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Constant Expressions

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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.

Decimal totalDue = 200 + 3;
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    IQueryable<string> salesInfo =
        from s in context.SalesOrderHeaders
        where s.TotalDue >= totalDue
        select s.SalesOrderNumber;

    Console.WriteLine("Sales order numbers:");
    foreach (string orderNum in salesInfo)
    {
        Console.WriteLine(orderNum);
    }
}

Dim totalDue = 200 + 3
Using context As New AdventureWorksEntities()
    Dim salesInfo = _
        From s In context.SalesOrderHeaders _
        Where s.TotalDue >= totalDue _
        Select s.SalesOrderNumber

    Console.WriteLine("Sales order numbers:")
    For Each orderNum As String In salesInfo
        Console.WriteLine(orderNum)
    Next
End Using

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.

See also