Matthieu MEZIL

Absolutely incredible! I don't know what else to say

Really good extension methods. msmvps.com/.../entityframework-include-with-func.aspx

Very cool!  I also hate using strings in this context: it seems counterintuitive, and very susceptible to mistakes.  At the same time, I'm not sure I'll be using this method.  Which of the following is easier for the next guy looking at my code to understand?

           Room room = ctx.Room

               .Include("Sessions.User")

               .Include("Sessions.Whiteboards.Owner")

               .Include("Sessions.Whiteboards.WhiteboardShape")

               .Include("Sessions.MediaStreams")

               .Include("Owner")

               .FirstOrDefault(r => r.OwnerID == ownerUserID && r.Name == roomName);

           Room room2 = ctx.Room

               .Include(r => r.Sessions.Include<Session, User>(s => s.User))

               .Include(r => r.Sessions.Include<Session, Whiteboard>(s => s.Whiteboards).Include<Whiteboard, User>(w => w.Owner))

               .Include(r => r.Sessions.Include<Session, Whiteboard>(s => s.Whiteboards).Include<Whiteboard, WhiteboardShape>(w => w.WhiteboardShape))

               .Include(r => r.Sessions.Include<Session, MediaStream>(s => s.MediaStreams))

               .Include(r => r.Owner)

               .FirstOrDefault(r => r.OwnerID == ownerUserID && r.Name == roomName);

They both do the same thing, but it requires a great deal more effort to understand what the second one is doing.  I don't like the first way at all -- but the second way is, if anything, uglier and more complicated.

That's not to say I don't appreciate the code -- I very much do!  You're trying to solve a problem that MS really should have solved itself.  There just doesn't seem to be an easy way to solve it.

Does anyone know if MS has addressed this in .NET 4.0?

@Ken, I too wish we had addressed this in .NET 4.0, but unfortunately it didn’t climb to the top of the priority list as we were implementing other features (i.e. POCO support, functions exposed in LINQ, model defined functions, T4 integration, FK support, Contains, DefaultIfEmpty, Single/First/OrDefault, better stored procedure support, ExecuteStoreQuery/Translate, OrderBy Lifting, improvements for StartsWith, optimizations for non-unicode columns, EntityDataSource improvements including LINQ support, etc).

It is hard to get any new feature in for .NET 4.0 at this point, but I promise I will bring it up for the next version.

I thinkk this is better:

public static ObjectQuery<T,K> Include<T>(this ObjectQuery<T> mainQuery, Expression<Func<T, K>> subSelector)

   {

var sb = new StringBuilder();

       FuncToString(sb, keyExpression.Body);

       return mainQuery.Include(sb.ToString());

   }

       private static void FuncToString(StringBuilder sb, Expression selector)

       {

           switch (selector.NodeType)

           {

               case ExpressionType.Parameter:

//                    sb.Append(((ParameterExpression) selector).Name);

                   return;

               case ExpressionType.MemberAccess:

                   FuncToString(sb, ((MemberExpression) selector).Expression);

                   sb.Append(".");

                   sb.Append(((MemberExpression) selector).Member.Name);

                   return;

           }

           throw new InvalidOperationException();

       }

And now you can use like this:

query.Include(c=>c.Session)

.Incude(c=>c.Session.User)

:)

Hello,

Thanks a lot for this code.

I was looking for something like that since I do not want to have strings for names sitting there too.

Now, I only have a strange problem: When I build a query and .Include it passes the data to the FuncToString routine as a ExpressionType.Convert (10) and not one of the three defined to work with.

I added another line to the case section, like this

Case ExpressionType.Convert

Return TryCast(TryCast(TryCast(selector, UnaryExpression).Operand, MemberExpression).Member, Reflection.PropertyInfo).Name (VB Syntax)

which is exactly the same as the .MemberAccess case except for another TryCase selector to UnaryExpression first.

I have no idea what I am doing there, how why what when, but it seems to work. Has anybody a hint why this change is needed, or what I was doing wrong in the first place? Why do I end up with ExpressionType Convert??

I have a second far harder question too: If you have two entities mapped m:n and the middle table of the database does not appear in your entity model (I like that...) I cannot get the function to work at all.

Any hint on that?

Thanks a lot!

Ralf

După *** spuneam în postul precedent , fiecare O/RM are propria metodă de a descrie graful de obiecte