Fine-grained control of deferred execution when implementing IQueryable<T>

I am implementing IQueryable, and so far have only implemented an expression visitor for 'Where' calls and everything else is currently unsupported. The expression is translated into native T-SQL. I plan on adding support for additional method calls over time, of course.

protected override Expression VisitMethodCall(MethodCallExpression m)
    {

        if (m.Method.DeclaringType == typeof(Queryable) && m.Method.Name == "Where")
        {

            sb.Append("SELECT * FROM (");

            this.Visit(m.Arguments[0]);

            sb.Append(") AS T WHERE ");

            LambdaExpression lambda = (LambdaExpression)StripQuotes(m.Arguments[1]);

            this.Visit(lambda.Body);

            return m;

        }

        throw new NotSupportedException(string.Format("Method '{0}' is not supported", m.Method.Name));

    }

Being that my 'Where' support uses deferred execution -- my question is whether it is possible and/or good practice to add support for other methods, such as 'Select', where under the hood deferred execution is not used, but its transparent to whomever is using the IQuery开发者_运维技巧able. So there is a working implementation until a deferred solution is available.

For instance:

var _query = dbContext.Products
  .Where(x => x.ProductName == "") // deferred execution
  .Select(x => new { ... });       // cast ToList() under the hood and proceed

So I guess my question is two-fold,

1) Is it possible / how easy is it to implement?

2) Is it even a good idea?

Thanks.

When something in Linq-To-Sql is not translatable to SQL it throws an exception. The programmer then has to consider that, and modify the method chain to include a call to .AsEnumerable first before calling such methods. IMO, that is more clear than doing so implicitly without the programmer knowing (by calling .ToList under the hood).