Last week I introduced a new screencast on another OData Developer tool. It was about how to use LinqPad to query OData service with C#, LINQ & WCF Data Services Client APIs.

The screencast shows how to use LinqPad to connect to and query OData Services using LINQ and WCF Data Services Client APIs. Showing how LinqPad can be useful as a developer tool to test queries against any OData Service.

I case you missed it, you can watch it on ODataPrimer website. You can also download an HD video (~48Mbs). The package contains 2 videos. One of them is the one hosted and it’s a 10 min video. And the other is ~14 min. I had to trim it to fit into youtube. The 14 min video contains additional stuff in case you are interested.

You can also subscribe to ODataPrimer channel on yourtube for future updates and videos.

Hope you’ll enjoy it.

Introduction

You might hear of KiGG, the open source project that is currently live as http://dotnetshoutout.com. I wanted to expose part of KiGG data as an OData Service for read only. But I figured out that exposing raw KiGG schema might not be useful. So I had to choose between 2 options that were up to my mind:

• Build some views on the physical store -database-. Create a new entity data model for those views and use the new data model context for DataServiceContext.
• Use Entity Framework 4.0 conceptual model function feature with complex types to simulate views. It’s like building views on the conceptual model itself and not the store model.

I picked the 2nd option. The sample downloadable sample is available at the end of this post.

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At the end of last month (27-28 Feb 2010) I got the opportunity to participate in Cairo CodeCamp event by giving a session about “Getting Started with Entity Framework 4.0”.

Here is summary of my session –taken from Cairo CodeCamp web site-:

An introduction to Entity Framework 4.0 that will be shipped as part of .Net 4.0 and VS.Net 2010. Exploring new and enhanced features of Entity Framework 4.0. Walking through building entity data model using VS.Net 2010 and Entity Framework 4.0. Examining new design features in Entity Framework introducing Persistence Ignorance.

I uploaded my session and demos. You can download them now. I hope you’ll enjoy the demos and presentation. Click here to download.

All sessions should be posted soon to Cairo CodeCamp web site. Keep tracked for updates.

I have a plan to record my session as screen cast in English and post it here as well. But can’t promise when this will be as I have many other things I committed to recently.

Keep tuned anyway you might find interesting stuff posted soon.

Introduction:

From the moment I put my hands on Visual Studio.Net 2010 Beta 1 and I’m targeting EF4 –Entity Framework 4- as I was very excited to checkout the new cool feature of it.

Here I am going to highlight my first look at Persistence-Ignorance support in EF4.

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On my previous post “What about DataLoadOptions for Entity Framework ObjectContext?” I was suggesting another way to define eager loading for Entity Framework. In this post I will introduce my DataLoadOptions for Entity Framework ObjectContext.

The beginning:

Actually Eager and Lazy loading on Entity Framework is not that much fun like in Linq to Sql. However this is going to be improved in EF4.

Here I will focus on eager loading and my slight improvement to define eager loading in Entity Framework. When I start to think about, I wanted something simple and pretty close to the way Linq to Sql work. In Linq to Sql it is the DataLoadOptions that helps you define eager loading before start using Linq to Sql DataContext.

So I started to explore the DataLoadOptions code using reflector, to better understand how it works and how it helps Linq to Sql define eager loading.

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I think the proper way to start this post is to ask How do you do eager loading with Entity Framework? And the basic native simple answer is by using ObjectQuery<T>.Include(string) method. No matter what you tried to do, you’ll end up using this way.

So there was ideas about how enhance the eager loading in our Entity Framework base applications. You can read about some of these ideas:

• Entity Framework Include with Func & Entity Framework Include with Func next by Matthieu MEZIL
• Typed Eager Loading Using Entity Framework (& What is Eager Loading vs Deferred Loading) by Meligy
• Fetching strategy posts by Simon Segal:
• Fetching Strategies for the Entity Framework - a waste of time for now?
• Entity Framework Repository, Specifications and Fetching Strategies
• The Entity Framework and a unified Lazy and Eager loading framework
• Entity Framework, Repositories, Specifications and Fetching Strategies Part 9.0
• Lazy Loading and Fetching Strategies again, with feeling!
• Lazy Loading and the Entity Framework. How long I can go on like this?

As I said, no matter what you tried, you’ll end up using ObjectQuery<T>.Include(string).

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I had few previous posts about DDD & TDD with Entity Framework that you might need to return to them before you proceed with this post. To summarize these posts, I was trying to build testable Models that is based on EF. But EF doesn't support Persistence Ignorance in its first version which make testing it in most cases require a database connection where you can test you code against it. My target was to build a testable models based on EF and that is independent of any underlying data source.

Introduction, Domain Model Review:

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I decided to provide some integration testing before proceeding as a proof of concept. In integration testing I will connect to the database and perform unit testing while connecting to the database.\

This unit test is almost identical to the one in my previous post. Except here I am testing the results that is coming out from EF and Database.

My target is to test IDataContext Implemented methods in NorthwindDataContext. Find below the Integration unit testing class. More...

In return to my previous posts about DDD & TDD with EF. I discovered few catches in my design that I wished to high light and discuss in this post. To summarize my take here are the head lines:

• What is the Responsibility of ObjectContext in EF?
• What is the Responsibilities of Repositories and whether they should be coupled with EF or not?

I come up with this post after few discussions through e-mail with Davy Landman.

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In previous post I talked about building domain model for Northwind using Entity Framework. I used the generated ObjectContext class which is NorthwindDataContext as the basic Data Access Layer Helper. But my NorthwindDataContext is implementing custom interface I created in order to be able to make my Data Access Layer testable as well as to be independent from EF.

My target is to achieve decoupling between EF and all layers above it. This include Repository classes. This might not be of a big benefit to everyone, because my repositories implementation will still dependent on IDataContext. But for me it will help to do TDD more smoothly regardless of my underlying data access layer. Beside it might allow me in future to be able to switch from EF to LINQ to SQL and just implement my IDataContext interface for LINQ to SQL.

Source code is attached to this post, feel free to download it and explore the code

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Introduction:

In my previous post I talked about definitions of TDD as specified in different sources. Here in this post I'll walk-through applied Domain Driven Design & Test Driven Design on Entity Framework.

I assume that you already know Entity Framework and how to create your entity data modes using Visual Studio.Net 2008 with SP1.

Domain Driven Design & Entity Framework:

To simplify things, I am using Northwind database. Basically I'll expose 3 tables in this database, Categories, Products & Suppliers. Those will be my domain objects as Category,Product and Supplier classes.

Each Category object might contain one or more items of Product. Same thing for Supplier object as it might provide one or more items of Product. That means Product object must have a Supplier and a Category. I defined those criteria for my Domain Objects.

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Me and Amr Elsehemy are working together in something and he requested a feature in some APIs I built. In fact he liked the Rob Conery's PagedList that had been modified by Troy Goode. He used it on his jBlogMVC post series about building Blog Engine using MVC.

That was pretty simple and I noticed something missing on the PagedList that I wished to add! What about sorting. I mean build a PagedList that is sorted. So I made slight changes to the enhanced PagedList made by Troy to support sorting.

Prerequisites:

It is required that you refer to Rob Conery's PagedList and the modified version by Troy Goode before you proceed in order to understand how this PagedList is useful and helpful with MVC and LINQ to SQL as well as LINQ to Entities.

Summary of changes:

To summarize the changes I made, simply I used Lambda Expressions to enable sorting. And had to modify Class declaration (with constructors) and the Initialize method. Sorting is provided by OrderBy extension method. Please return to method documentation for more details.

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In my previous post I talked about what is not supported in LINQ to Entities and made a simple comparison with LINQ to SQL show that these unsupported things works fine in LINQ to SQL.

Here I am going to provide workarounds these things. First one will be wrapping the entities with Business Classes. And the second way will be using client evaluation which is converting to work with LINQ to Object. Before you go further, I recommend that you read my previous post to save your time.

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Recently and after .Net 3.5 SP1 & Visual Studio.Net 2008 SP1 released, I started to play with LINQ to Entities. Really Entity Framework is interesting. Maybe not the best ORM tool, but still it is interesting and easy to use plus it is all one IDE at the end.

At the same time I was watching screen-casts made by Rob Conery about Building MVC Storefront along with TDD. In fact he was using LINQ to SQL. And I liked his coding techniques presented in his sample application and screen-casts.

I decided to play around with LINQ to Entities with MVC. Here I am going to talk about my adventures with LINQ to Entities, and really it is completely different from working with LINQ to SQL.

My recommendation for every developer is to start by reading Supported and Unsupported Methods (LINQ to Entities). Yes it will save you sometime. Do You know LINQ to SQL? Then you are familiar with LINQ. But you need to know what there and what is not there in LINQ to Entities. This even Might help you to build a wish list for LINQ to Entities also ;O).

Here I'm going to use some code samples presented in MVC Storefront and show some of the techniques that will not work with LINQ to Entities. And I will compare code with LINQ to SQL. In some other post, I'm going to present some other workarounds provided by ADO.NET Team when I asked them about the issues I have with LINQ to Entities. Also I'll present my own workarounds. And I'll compare the Generate SQL statements. I am not query optimizer, so I will not say what is the best choice. But you can help me in that.
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