OrderBy(): I need to page records, but I don't care about the order: How to specify a default KeySelector?

Question

I need to page records but I don't know the Entity's fields. Any way to OrderBy the Key (whatever it is) or simply specify some default OrderBy Lambda?

For example, I can do this with the Where Clause without knowing the Entity's properties:

 var myRecords = DC.Products.Where( p => p);

This is a case where the Skip and Take require an OrderBy, but I don't know the Entity's Key fields.

EDIT:

When I don't have OrderBy() when using Skip().Take(), I get this error:

The method 'Skip' is only supported for sorted input in LINQ to Entities.
The method 'OrderBy' must be called before the method 'Skip'.

Answer 1

For getting the Key property name, you would have to leverage the MetadataWorkspace object. Once you get the name from it, you can build a dynamic query with EntitySQL to get the results or using the Query Builder methods to build an EntitySQL for you, like I showed below, they are just like LINQ to Entities methods except that they accept string instead of Lambdas:

var keyName = context
    .MetadataWorkspace
    .GetEntityContainer(context.DefaultContainerName, DataSpace.CSpace)
    .BaseEntitySets.First(meta => meta.ElementType.Name == "Product")
    .ElementType.KeyMembers.Select(k => k.Name).FirstOrDefault();

    var query = context.Products.OrderBy("it." + keyName);
    var anotherQuery = context.Products.Where("it." + keyName + " = 1" );

Answer 2

If you didn't need any order do this:

myList.OrderBy(o=>1==1).Take(10)

but if order is important define an interface with just one property (name it ID), and implement this interface in all of your items, and do orderby on ID