What's the convention for extending Linq datacontext with set based helper operations specific to one collection of entities only

Question

Hi All

I might be vaguing out here but I'm looking for a nice place to put set based helper operations in linq so I can do things like;

db.Selections.ClearTemporary()

which does something like

db.DeleteAllOnSubmit(db.Selections.Where(s => s.Temporary))

Since I can figure out how to extend Table<Selection> the best I can do is create a static method in partial class of Selection (similar to Ruby) but I have to pass in the datacontext like;

Selection.ClearTemporary(MyDataContext)

This kind of sucks because I have two conventions for doing set based operations and I have to pass the data context to the static class.

I've seen other people recommending piling helper methods into a partial of the datacontext like;

myDataContext.ClearTemporarySelections();

But I feel this makes the dc a dumping ground for in-cohesive operations.

Surely I'm missing something. I hope so. What's the convention? TIA

Answer 1

public static class LinqExtensions
{
  public static void Clear<T>(this Table<T> t, Expression<Func<T,bool>> pred)
  {
    t.DeleteAllOnSubmit(t.Where(pred));
  }
}

Usage:

db.Selections.Clear(x => x.Temporary);

If needed, the DataContext can be accessed from a Table<T>.

Answer 2

I'm thinking of creating nested classes as partials of the datacontext plus a getter that initializes and returns the nested class

public SelectionsHelperClass SelectionsHelper {
  get {
    return new SelectionsHelperClass(Selections)
  }
}

This way I can do db.SelectionsHelper.ClearTemporary() without passing in the context while keeping set based operations (collection operations) specific to Selections logically together. I haven't tested this.

Something I forgot to mentioned is that reason I want these helpers is that they are frequently shared by some but not all controllers in an asp mvc app and I'm looking for a place to refactor them too.