Note: This is not about the difference between Database first, Model first, and Code first.
Microsoft has a number of tools to simplify using DbContext. Unfortunately, there seems to be almost no description and also no documentation on what they are, much less what they do.
What is the difference between:
Entity Framework Power Tools CTP1
ADO.NET C# DbContext Generator
ADO.NET C# POCO Entity Generator
I don't usually answer my own questions, but here is what I figured out:
The difference between the ADO.NET C# DbContext Generator and the ADO.NET C# POCO Entity Generator is that the former creates a context based on the DbContext and the latter creates them based on the ObjectContext.
Basically, these are used in the Model First and Database First approaches. The difference between Model First and Database First is that in Database First, you define your data model in the database, then reverse engineer the model (ie. create an .edmx file) from the database. While with Model First, you create your model in the designer (again, the .edmx file) or by hand, then generate the database from that model.
In both cases, you then generate POCO classes and either a DbContext or ObjectContext from the .edmx file.
The Entity Framework Power Tools CTP1 reverse engineers a Code First model from the database, including POCO class, the DbContext (don't think it offers ObjectContext generation) and the mappings (via the OnModelCreating method).
So what this boils down to is that in Database First and Model First, the "model" is defined by the xml .edmx file (or in some cases, several files). While in Code First, the model is defined using fluent code mappings in OnModelCreating.
When using the Power Tools to reverse engineer the database, it doesn't create an .edmx file, instead creating the mappings in code. Thus, skipping the xml middle man.
ADO.NET C# POCO Entity Generator exists for a long time and is part of the Mode First approach. Read about it here.
The differences between ADO.NET C# POCO Entity Generator and ADO.NET C# DbContext Generator are discussed here: ADO.NET DbContext Generator vs. ADO.NET Poco Entity Generator (ObjectContext).
Entity Framework Power Tools CTP1 is a drop of useful tooling for the project's context menu.
Related
How tightly can the ORM data classes generated by LINQ to SQL be integrated with the Model layer in MVC? Could these ORM data classes act directly as the model, if so, how would validation occur as it is usually done in MVC 3 with DataAnnotations? It seems that it would be diffiult to add these to the generated classes.
Separation of Concerns suggests that the classes that make up your domain model shouldn't be dependant on the technology that's used to implement your Data Access Layer, so I make every effort to ensure that they're not propogated through the UI.
If you use Entity Framework instead of Linq-to-SQL, you can use the POCO generator instead of EF's default EntityObjects. While these are still generated from the EF database model, you can replace the data access implementation but retain the POCO's for your domain model.
I'm trying to design application that will have UI with database in the backend.
I will be using Linq-to-SQL as the database layer to update and insert.
Now I'm trying to find out the best practice to use in designing the project, suppose I have 2 tables in the DB (Customers, Orders)
Shall I depend on the generated Linq-to-SQL classes, or shall I still create classes for Customers, Orders?
Shall I wrap the generated Linq-to-SQL inside another class to add validations?
I hope my questions are clear.
L2S is in my opinion an excellent light-weight data access method. If you have control over the database and have limited application data processing logic it is often a good choice.
If you have a two-tier app with a UI communicating directly with the DB then you can depend on the L2S generated classes. If you have a multi tier app with a client communicating with e.g. a WCF service you probably need Data Transfer Objects.
Use the partial methods on the L2S classes for validation.
I think you should use other ORMs for better implementation DAL for example Entity Framework or Nhibernate this ORMs allow you Model First approach without attributes
and the validation logic you should separate in other classes for exmaple MyEntityValidator
And also good approach to use the Repository pattern this pattern allow doesn't depend on Data access EF or Nhibernate
and look at this Entity Framework and Repository
Using LINQ to SQL make application development faster but dissolves the logical layers in the application. The data access layer and the business objects layers almost have no identity, they sit in the same dll. Does any one has an idea on how to develop an enterprise level application using LINQ to SQL. How do we cleanly separate the business object and the LINQ generated entities ? How would they communicate, how would data be transferred between our business objects and LINQ entities. Any article or any suggestions towards this would be greatly appreciate. Thanks.
We're using L2S for our next generation of software that manages our plant operations and related applications. This is for a $2.5B thin film solar company. We have built a clearly defined L2S based n-tier application framework.
We also created our own code generator to generate an application set of entities, a L2S set of entities, a business logic layer and data access layer. The L2S set of entities is for back-end use only. The application entities (which have no L2S plumbing built in) is for transferring data back and forth from application to server. We use WCF for application tier to server tier communication.
Our applications use WCF to call to the back-end businss logic layer for data processing. The business logic layer calls to our data access layer for low level Linq based data access. Our application entities get passed to and from our back-end. In the back-end, we have very efficient mapping that maps an application entity to each L2S entity.
Works very well for us.
Randy
You can get very far with L2S (as StackOverflow has proven), but IMHO Linq2SQL is not well suited (nor intended, I think) for "enterprise level applications".
Now that Entity Framework 4.0 has been released, you may want to consider going with EF instead. It supports POCO and will allow you do have a much nicer layered architecture.
Check out:
The ADO.NET Entity Framework
ADO.NET C# POCO Entity Generator
I recently ported a substantial code base from L2S to EF 4.0. Since EF now supports lazy-loading, you can have a very smooth transition from L2S to EF, leveraging the advanced features of EF only when you need them.
In the NerdDinner example they use a repository pattern to decouple the business from the data layer. But then they use the Linq to SQL generated classes (Dinner specifically) as the entity class used throughout the project. So how decoupled is that really? It’s not like you could easily exchange Linq-to-SQL.
On my last project I created a separate entity class that I populated with left/right in the linq query because I found that even if you use a partial of the linq generated you cannot populate any additional fields that you add at query time.
LINQ to SQL is strongly tied to the database schema, which is why I wouldn't use it. I'd use Entity Framework instead, as it permits a mapping between the conceptual and logical models.
I would like to know what are the principal diferences between "ADO.NET Entitiy Data Model" and "Linq to SQL Classes"? What is the best choice to work with?
I couldn't find any document on the internet explaing that and everything I know is that we can use both, "almost", in the same way.
Linq To Sql is not being actively supported by Microsoft anymore.. They have picked the Entity framework has 'the way for the future'. You can google and verify this.
Here's your friendly neighbourhood SO topic with all the good bits
Update: Hmm.. it seems that MS has taken a step back from the infamous declaration. But the message is still not clear with respect to the future of L2S.
as of .NET 4.0, LINQ to Entities will
be the recommended data access
solution for LINQ to relational
scenarios.
We also want to get your feedback on
the key experiences in LINQ to SQL
that we need to add in to LINQ to
Entities in order to enable the same
simple scenarios that brought you to
use LINQ to SQL in the first place.
That pretty much reads 'phasing out' to me. I may be guilty of reading between the lines though.. there may be hope after all... behind all the 'on-the-fence' answers
ADO.Net team blog : Update on LINQ to SQL and LINQ to Entities Roadmap
ADO.Net team blog : Clarifying the message on L2S Futures.
http://damieng.com/blog/2008/10/31/linq-to-sql-next-steps
EF classes are not persistent-ignorant. They inherit from a base class that adds a unique entity key and change tracker. This can make disconnected environments more of a pain with EF than the object generated by L2S.
This is what I can tell from personal experience (which may not be the whole story):
The learning curve for LINQ to SQL may be slightly less steep than for ADO.NET Entity Framework. Personally, I also feel that LINQ to SQL is a bit more lightweight.
Both frameworks are getting updated in the next version of the .NET framework (version 4).
If you include the features for .NET 4 then Entity Framework appear to be the more feature rich framework. Microsoft seems also very commited to this framework.
Visual Studio has quite strong support for both frameworks. For instance, if you create an ADO.NET Data Service in your project it will discover both your LINQ to SQL and Entity Framework classes.
Entity classes in the Entity Framework are derived from a specific base class in the Entity Framework. Some may consider this a showstopper for using the Entity Framework.
I find both frameworks surprisingly easy to use and I would suggest anybody interested in these technologies to play around with them. Create a .NET project of choice in Visual Studio and add both LINQ to SQL classes and an Entity Framework model connected to whatever database you have access to. Then try out both frameworks by doing things like CRUD operations etc.