How to check for the presence of an OrderBy in a ObjectQuery expression tree

Question

I\'m using T4 for generating repositories for LINQ to Entities entities.

The repository contains (amongst other things) a List method suitable for paging. The docum

Answer 1

Thanks to David B I've got a the following solution. (I had to add detection for the situation where the partial method was not executed or just returned it's parameter).

public partial class Repository
{
    partial void ProvideDefaultSorting(ref IOrderedQueryable currentQuery);

    public IQueryable List(int startIndex, int count)
    {
        NorthwindEntities ent = new NorthwindEntities();
        IOrderedQueryable query = ent.CategorySet;
        var oldQuery = query;
        ProvideDefaultSorting(ref query);
        if (oldQuery.Equals(query)) // the partial method did nothing with the query, or just didn't exist
        {
            query = query.OrderBy(c => c.CategoryID);
        }
        return query.Skip(startIndex).Take(count);
    }
    // the rest..        
}

public partial class Repository
{
    partial void ProvideDefaultSorting(ref IOrderedQueryable currentQuery)
    {
        currentQuery = currentQuery.Where(c => c.CategoryName.Contains(" ")).OrderBy(c => c.CategoryName); // compile time forced sotring
    }
}

It ensures at compile time that if the partial method is implemented, it should at least keep it an IOrderdQueryable.

And when the partial method is not implemented or just returns its parameter, the query will not be changed, and that will use the fallback sort.