Performing part of a IQueryable query and deferring the rest to Linq for Objects

Question

I have a Linq provider that sucessfully goes and gets data from my chosen datasource, but what I would like to do now that I have my filtered resultset, is allow Linq to Objects

Answer 1

The kind of thing that I was after was replacing the Queryable<> constant in the expression tree with a concrete IEnumerable (or IQueryable via .AsQueryable()) result set...this is a complex topic that probably only makes any sense to Linq Provider writers who are knee deep in expression tree visitors etc.

I found a snippet on the msdn walkthrough that does something like what I am after, this gives me a way forward...

using System;
using System.Linq;
using System.Linq.Expressions;

namespace LinqToTerraServerProvider
{
    internal class ExpressionTreeModifier : ExpressionVisitor
    {
        private IQueryable queryablePlaces;

        internal ExpressionTreeModifier(IQueryable places)
        {
            this.queryablePlaces = places;
        }

        internal Expression CopyAndModify(Expression expression)
        {
            return this.Visit(expression);
        }

        protected override Expression VisitConstant(ConstantExpression c)
        {
            // Replace the constant QueryableTerraServerData arg with the queryable Place collection.
            if (c.Type == typeof(QueryableTerraServerData))
                return Expression.Constant(this.queryablePlaces);
            else
                return c;
        }
    }
}