If you are not using “Lazy Loading” on Linq to SQL or EF, you have to join other tables using Include(“”) statement. Worse thing about this extension it takes string argument. If you change the db schema then you have to be careful about those Include statements. recheck all of them or you have to rely on unit tests (That’s why we need unit testing).

Damien Guard made an excellent solution for this particular problem. You can use his extension as strongly-typed include statements.

Here is the extension method:

public static IEnumerable<T> Include<T, TInclude>(this IQueryable<T> query, Expression<Func<T, TInclude>> sidecar) {
   var elementParameter = sidecar.Parameters.Single();
   var tupleType = typeof(Tuple<T, TInclude>);
   var sidecarSelector =  Expression.Lambda<Func<T, Tuple<T, TInclude>>>(
      Expression.New(tupleType.GetConstructor(new[] { typeof(T), typeof(TInclude) }),
         new Expression[] { elementParameter, sidecar.Body  },
         tupleType.GetProperty("Item1"), tupleType.GetProperty("Item2")), elementParameter);
   return query.Select(sidecarSelector).AsEnumerable().Select(t => t.Item1);
}

Here is an example:

var oneInclude = db.Posts.Where(p => p.Published).Include(p => p.Blog));
var multipleIncludes = db.Posts.Where(p => p.Published).Include(p => new { p.Blog, p.Template, p.Blog.Author }));

Excellent solution. Check it out.