In the earlier bits, if you changed an association to an inhertiance, the type that becamse the derived type lost its mappings and th emappings for any associations.

Depending on how complex that type is, recreating all of that could be challenging.

I just tried this out in the new bits and the mappings and association mappings all remain intact.

This is great and it will save a tree too, since I can go remove all of that explanation about how to deal with that problem from Chapter 5 of my book!

If you have screwed up your Entity Data Model, you may be familiar with safe mode when you try to open the model up in the designer.

But the mapping designer has Safe Mode now, too.

Here is what I get when I am in the middle of creating an inheritance in my model which means that some of my mappings are still a big goofy. I tried to get to the mapping details of the derived type and here is what I see:

The error messages for Entity Framework and the designers are really very helpful.

Over a year ago I asked a question in the EF forums about being able to use strings in conditional mapping.

It is now possible! Yay.

Having just done a presentation at DevTeach called “.NET 3.5 Data Access Guidance”, which I will be doing again at TechEd in a few weeks and I have a CoDe Magazine article on this topic coming up as well, it is definitely interesting to me to see what is probably the first somewhat official looking (it’s a blog post, not a white paper) guidance from someone at Microsoft about Why to use Entity Framework.  Outside of a direct comparison of LINQ to Entities vs LINQ to SQL by Elisa Flasko earlier this year , there hasn’t been a Microsoft white paper on Entity Framework since June 2006. That’s almost 2 years. And that was written when they were first going public with the technology. What Danny is doing here is definitely a first.

In my presentation/article I need to be objective. Granted I am only addressing what’s “in the box” – datasets, LINQ to SQL and EF, not nHibernate/ORMs. And I have to be sure not to lean towards EF, which is difficult not to do since I am so focused on it.

But Danny’s list is definitely right on. He is highlighting the benefits of EF compared to datasets, compared to LINQ to SQL and also compared directly to nHibernate. It’s funny how we (Danny, myself, maybe others) tend to include nHibernate, which has a LOT less users than datasets or LINQ to SQL in these discussions because it is the [relatively] small # of nHibernate users that make the most noise and Danny and I have both been beaten up quite a bit by them, so we now have a natural tendency to be sure to address them at every turn. I think it’s become self-defense measure more than anything else. (I shouldn’t really speak for Danny here, since he may have different reasons. I know that this is true for me, though.)

One thing that I need to do differently than Danny’s post when I do the overall guidance presentation is not just list the places where EF totally outshines the other options, but I also need to address areas where you may prefer the others.

Every time I have done this guidance presentation, I have had someone say to me after the fact, “but I really love typed datasets? Why should I move to EF or LINQ to SQL”. My response to them is that if after seeing my presentation, if there is nothing that was truly compelling to them to want to make the change, then typed datasets are probably just the right choice for them.

When VS2008 SP1 beta was released on Monday, I was getting ready to head for Toronto to present three sessions at DevTeach which would be on Wednesday and Thursday. One session was on Astoria another touched LINQ to SQL/EF and DataSets and the last was a deep dive into EF with respect to tiered programming.

The new bits would impact these talks, especially the Astoria and deep dive EF talk a lot and I truly did not want to show people what were now incorrect namespaces, classes whose names had changed, Entity Graphs that did not serialize with services, etc etc.

I made a scary decision and took a huge risk. I updated all of my demos to align with SP1 – this  I did on my dev box at home. This was more than a matter of tweaking some EDMX files and changing class names. The tiered applications needed to be completely reconsidered, rearchitected and rewritten. When I had gotten far enough in this process that I was confident I could finish the transition up, I knew it was time to get the SP1 bits onto my presentaiton laptop.

This didn’t go so well. I started the install just before I headed off to my user group meeting. Six hours later I returned to see the install failed because the vista windows sidebar was on. This was 10:30pm. I worked at trying to get the new bits installed until 9am the next morning and then had to give up and head for the airport. To be safe, I threw my CPU, which had what I needed, into my suitcase!

At the speaker dinner that night in Toronto, I was offered a VPC by scott Hanselman who is my savior for the month of May. It already had Vista on it, with VS2008, the Service pack and even Fiddler which I needed for the Atoria session. It was a full day since I began this installation. I hadn’t slept and I hadn’t been able to complete the demo transitions but I was fully committed.

Or perhaps should be committed.

I pushed my EF debugging skills full bore. But there was more to deal with since the VPC wasn’t quite the same as my setup. I had to install all of my databases and change all of the connection strings (there were a lot) inthe many many projects for the 3 sessions in addition to running thorugh every single demo to see where things weren’t working.

I didn’t get everything fixed on  time and had to go into my presentations knowing that I’d have to skip a few demos and hoped that the bulk of the attendees would feel the same as I did about being able to see how things are not how things were. I think the feelings were mixed (sorry to anyone who found my decision not to be the best).

There is still one entity sql query that is driving me nuts. It keeps saying that “customer” doesn’t exist, though the query looks at Customers. Almost as though I had cached something.

I got a few hours of sleep, had chocolate and coffee as my critical helpers, bit the bullet and went for it.

But boy oh boy, I’m not sure if I really need this kind of excitement in my life! 🙂

I still need to tighten the rest up so I can get the demos up ontot he DevTeach website, but since not many of the session attendees have SP1 installed yet, hopefully they won’t mind waiting a few days.

The Astoria Team has provided a very impressive list of what’s changed and what’s new in the new bits for Astoria that were released with VS2008 SP1 today.

I was surprised to see they already have the Batching and Optimistic Concurrency stuff in there that they were only just recently considering.

Here are my own notes from trying to get an Astoria demo working before I had access to the nice list that is now available.

1) If you are using an Entity Framework EDM as your data source , there are some easy to fix (and easy to discover) breaking changes to the model.

See this post on my notes for updating an Entity Framework solution to SP1.

2) The service file is very different. You will be best to create it from scratch then move your logic into the new SVC file.

3) Namespaces and classes have changed.

• Microsoft.Data.WebClient namespace becomes System.Data.Services
• WebDataContext becomes DataServiceContext
• WebDataQuery becomes DataServiceQuery

4) Methods for limiting access and the enums have changed

OLD config.SetResourceContainerAccessRule("*", ResourceContainerRights.AllRead);
NEW config.SetEntitySetAccessRule("*", EntitySetRights.AllRead);

SetServiceOperationAccessRule stays the same

5) WebDataGen is now DataSvcUtil and can be found in C:\Windows\Microsoft.NET\Framework\v3.5\DataSvcUtil. The parameters for this were simplified, too.

I recommend using DataSvcUtil to recreate any classes you want to use in Astoria clients. I actually fixed one up manually before I found DataSvcUtil and it was a pain.

6) The Attribute used to identify the Key field (needed when the field names are not discoverable by Astoria) has changed.

It was <System.Web.DataWebKey()> and was used on the property.

Now it is System.Data.Services.Common.DataServiceKey(propertyname) and is used on the class. It can also take an array of strings if there are multiple keys.

7) The Silverlight and AJAX client libraries are not included with these bits but the AJAX one is  on CodePlex.

That’s two of my four demos from my Astoria talk. I’m currently trying to figure out how to retrofit the old ajax data services library into a new application.

http://www.codeplex.com/aspnet/Release/ProjectReleases.aspx?ReleaseId=13357

There are probably lots more goodies in there, but these notes represent the pain I had to go through to get my Astoria demos that I’m doing this week at DevTeach working again.

Along with Soma and others, the ADO.NET team has announced that the next beta of Entity Framework is available with the VS2008 Service Pack 1 BETA bits. The Astoria team already has a list of changes on their blog and there will be one coming for EF as well.

In the meantime….

Never a dull moment. I have two EF sessions this week at DevTeach and have to very quikly overhaul my demos.

Here are some of my notes.

EDMX Changes

Designer section

<edmx:ReverseEngineer /> has to be removed. I guess it was hopeful thinking.

SSDL

New attribute required inside of schema (Provider=”System.Data.SqlClient”)
These attributes had to be removed: DateTimeKind=”Unspecified” PreserveSeconds=”true”
ProviderManifestToken Attribute in schema declaration needs to be changed from the version number (eg for SS2005 that was ProviderManifestToken=.09.00.3054 now is ProviderManifestToken=2005.

Designer section is now at the bottom of the file. Nice.

You cannot have both the Design view and the XML view of an EDMX open at the same time.

In the Model Browser window, the XML for various pieces of the model are no longer shown in the tool tips. While there are reasons behind this, I REALLY liked this and am sad to see it go. Now I have to always close the designer and open up the XML and trudge through it if I just want to verify something. Oh well.

Designer Changes

Oh my its pretty! It’s cleaned up; the Asscoiation names are no longer clogging up the view, it’s more flexible wrt to what’s available on context menus and it has some nice shortcut icons for zooming etc.

Update from Model

As per a blog post from Noam Ben-Ami a while ago, this has improved enormously. With some minor excpetions (which I have not experienced) the CSDL stays intact when you update even though teh SSDL will be competely rewritten so any changes there will be lost. If you add new fields to a table in the database, and it’s obvious in the model where it should go, it will make it into the CSDL.

Code Generated Classes

Best bet: just delete them and let VS2008 regenerate them.

API Changes that I’ve experienced so far

It is very nice to have full graphs coming in and out of WCF services. 🙂

Believe it or not, I haven’t run into anything else so far that has impacted my apps except for the fact that I need to completely rearchitect my WCF solutions now that I have graphs to pass back and forth. Will I get this done before my session on using Entity Framework across tiers on Wednesday? Nothing like being forever behind the 8-ball. 🙂

The EntityDataSource control

I am not a big fan of drag & drop, but I’m liking this control so far. Here are some of the things that are winning me over.

Easily use inherited types

Easily do eager loading with the IncludePaths property.
Note: There’s a bug which is preventing the combination of eager loading when you are using an inherited types. That will go away with the next available build.

Many opportunities to override behavior. There are lots of events and the most important to me (so far) is the one lets me control what context the control will be tied to. By default, every EntityDataSource spins up its own context. That’s not good if you want to have relationship management happening.

Dynamically build queries with the properties or just entier an EntitySQL string as the command text.

Note that the where parameter takes an Entity SQL predicate, just like you would use with Query Builder methods.

That’s all for now.

Have fun!