Question

I would like a sample of code.
At the moment I use linq in c# and asp.net 4 ef4

       var querySlotOrder = from slot in context.CmsSlots
                             where slot.SlotId == myCurrentSlotId
                             select slot;

           if (querySlotOrder.SlotOrder == myNewSlotOrder)
                e.Cancel = true;

This linq query return only a record.

Using VAR I cannot get the Typed Object and I cannot access its property SlotOrder.

How to change the query? thanks for your help

Usefully resource on the topic:

http://msdn.microsoft.com/en-us/library/bb384065.aspx

http://msdn.microsoft.com/en-us/library/bb397947.aspx

http://msdn.microsoft.com/en-us/library/bb397678.aspx

Answer 1

Even if your query returns a single object, the Select method, which you are using behind the scenes, doesn’t. It returns an IQueryable<T> in EF.

You should use a method such as Single, SingleOrDefault, First, FirstOrDefault if you want to store a single object.

var querySlotOrder = (from slot in context.CmsSlots
                      where slot.SlotId == myCurrentSlotId
                      select slot).Single();

The difference between the four methods is:

• Single: Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.
• SingleOrDefault: Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
• First: Returns the first element of a sequence.
• FirstOrDefault: Returns the first element of a sequence, or a default value if the sequence contains no elements.

(Definitions from MSDN)