Query: Consider adding method to force client evaluation of an expression

[divega]

The fix for #12697 enables using a method defined like this in a query:

public static T Client<T>(T s) => s;

The point being that the method is opaque to our query translator and therefore forces client evaluation. I want to suggest that we consider adding a method like that somewhere under the static EF class for better discoverability.

I haven't tested how well it works and I am not sure I understand all the implications but ideally this could be used both on the way in (to force funcletization of an expression that would otherwise be translated, i.e. a shortcut for having to write the expression outside the query) and on the way out (force client evaluation of an expression that would otherwise be translated).

Example usage:

                var data = (from c in db.Checks
                                 join ct in db.CheckTemplates
                                      .Include(a => a.Implementers).ThenInclude(u => u.User)
                                 on c.CheckTemplateId equals ct.CheckTemplateId
                                 where c.CheckId == checkId
                                 select new
                                 {
                                     CheckId = c.CheckId,
                                     Description = ct.Description,
                                     Implementers = EF.Client(ct).Implementers,
                                     NumExaminers = ct.Examiners.Count
                                 };

[pmiddleton]

Could users misunderstand the feature and try passing a lambda to the Client method that references column data? That won't be executable client side.

[divega]

@pmiddleton that is a reason to come up with a good name. Worst case that would cause N+1 queries (or throw).

[ajcvickers]

Tracking this as part of 3.0 query behaviors, so added to #12795