Question

I have a linq-to-sql query over entity that has child entityset that I need to sort on some child fields, i.e. use this query:

   var query = from p in context.Patients 
            let order = p.Lab_Orders.First() 
            orderby order.Order_Date 
            select p; 

This query runs fine, but how would I modify it to use DLINQ OrderBy method what would I pass as a sorting parameter in run-time?

Answer 1

If by DLINQ you mean Dynamic Query, then you can’t use the query expressions like that, you have to use extension methods with lambdas. You can start with a query expression but you have to eventually switch it over to lambda:

IEnumerable<Patient> GetPatients(string orderSortField)
{
    var query =
        from p in context.Patients
        select new
        {
            Patient = p,
            FirstOrder = p.Lab_Orders.First()
        };
    return p.OrderBy(orderSortField).Select(p => p.Patient);
}

Call it with:

var patientsByOrderDate = GetPatients("FirstOrder.Order_Date");