How select subset of columns from IQueryable<Type>?

Question

From my business tier (class) I get back an IQueryable<Pen> of data.  Here is my client code that works fine:

 

PenClass penClass = new PenClass();
IQueryable<Pen> pens = penClass.SelectPens();

However, I want to then select a subset of this data from within the client.  I tried this:

 

IQueryable<Pen> pensSubset = from p in pens select p.PenId, p.PenNumber;

 

.. but it doesn't even compile.

 

Can anyone tell me the correct syntax?

 

Thanks.

 

Answer 1

You need to define a class for this purpose:

public class PenCore { public int PenID, PenNumber }

and then project into it:

IQueryable<PenCore> pensSubset =

from p in pens
select new PenCore
{

PenID = p.PenId,
PenNumber = p.PenNumber

};

You can then return Queryable<PenCore> from your method. Another option is to use an anonymous type, but this is viable only if you don't intend to pass that data between methods.

Joe

Answer 2

VB supports the inline select statement as you specified, but C# requires the type initializer syntax Joe mentioned.

 

Jim Wooley

www.ThinqLinq.com