I was watching some videos and tutorials for EF 4.1, and I do not understand any benefit of CodeFirst (except some if DB is very small 3-4 tables and I am lazy for creating DB first).
Mostly, the best approach so far is to create Database in some sort of Database editor, which is sure faster then editing in the Entity Model and EF picks up every relationships and creates associations correctly. I know there are challenges in naming convention etc, but I feel its very confusing to manage Code First as everything looks like code and its too much to code either.
What is it that CodeFirst can do and Db first cannot?
CodeFirst cannot do anything that DB first cannot. At the end of the day they are both using the Entity Framework.
The main advantages of using codefirst are:
Development Speed - You do not have to worry about creating a DB you just start coding. Good for developers coming from a programming background without much DBA experience. It also has automatic database updates so whenever you model changes the DB is also automatically updated.
POCOs - The code is a lot cleaner you do not end up with loads of auto-generated code. You have full control of each of your classes.
Simple - you do not have a edmx model to update or maintain
For more info see Code-first vs Model/Database-first
and here Code-First or Database-First, how to choose?
Coming from a DataCentric approach, I will always find it strange the people like to create in a Code First Approach. When I design my database, I am already thinking about what each of the tables are as if they were classes anyway. How they link together and how the data will flow. I can image the whole system through the database.
I have always been taught that you work from the ground up, get your foundations right and everything else will follow. I create lots and lots of different systems for lots of different companies and the speed that I do it is based on the fact that once I have got a strong database model, I then run my custom code generator that creates the Views/Stored Procedures as well as my Controller/BusinessLayer/DataLayer for me, Put all of these together and all I have to do is create the front end.
If I had to create the whole system in code first to generate the database, as well as all of the other items then I would image it taking a lot longer. I am not saying that I am right in any terms, and I am sure that there are probably faster and more experienced ways of developing systems, but so far, I haven't found one.
Thanks for letting me speak and I hope my views have helped a little.
Migration was enabled in EntityFramework 4.3 for CodeFirst , so
you can easily update changes from model to the database seamlessly Reference 1
detailed video:Complete Reference Video
Well, it depends on your project. I'll try to make a synthase some ideas:
You have total control on the entity classes. They are no more generated, you don’t have to update T4 templates or use partial classes…
EDMX model will disappear in EF7 in favor of CodeFirst model. So keep in mind if you plan to migrate to EF or you have projects start in the near future that could use EF7.
Easier to do merge in case multiple devs are working on the model
+/- Annotations and mapping should be done manually. I would say code first approach seems lighter (less bloat) and we can keep things simple (visual model could hide undesired complexity). Open to Fluent API.
You can still visualize model via Power Tools, but the model is read-only. Any change to the model should be done manually (even the initial entities can be generated from scratch). You don’t have partial models (diagrams), but our models should be small enough.
It seems database first is better integrated with SPs and function results (some improvements have been done in EF6)
Related
I'm recently migrating to Linq2Sql and all my future projects will be using Linq2Sql. Having said that, I researched a lot on how to properly plug-in Linq2Sql in application design.
what to put at what layer ?
How do you design your repositories and business layer services ?
Should I use DTOs over Linq2Sql entities on interaction layer ?
what things should I be careful about ?
what problems did you face ?
I did not find any rock-solid material that really talked about one single thing and everyone have their own opinions. I'm looking forward to your ideas on how to integrate/use Linq2Sql in projects. My priority is maintenance[it should be maintenable and when multiple people work on same project] and scalabilty [it should have scope of evolution].
Thanks.
I have been using linq to entities for the last two and half years on production applications and I can say it has been a really nice experience... but that doesn’t means you should do everything with Linq.
I am going to try to give you some answers to your questions,
I think you should ask first what kind of application you want to create; once the scenario is clear you will have an odd idea of number of transactions or queries you are going to perform against the database (or repository).
Linq could be extremely useful to abstract data access, context and entities handling, but everything comes with at a cost. Objects will be created with a cost and you really need to think about this.
If your application has a ‘nice-not-too-heavy’ data access Linq will be the perfect tool to save time for your application.
If your application is entirely based on data extraction or processing, Linq will be great as well.
If your application is handling huge blocks of data (check your application) you will need to do something else to avoid creating a bunch of objects that might be useless.
What does that means? You need to know what a smart data access means... and that is leave SQL to work for you (in the case of SQL); if you are going to do lots of joints, cross information and stuff, create stored procedures that creates the data result for you and then get it using Linq or SqlCommand or SqlDataAdapters, etc...
What to put at what layer?
Since Linq gives you the data access abstraction you can pretty much place your code where the business logic demands it. There are tons of good practices of how to structure your code; Linq (as any other entity framework or data access libraries) will fit in the right spot.
Avoid whenever is possible direct linq expression in your controls (asp.net has lots of controls with linq data sources), instead wrapped your ‘query’ with a service class that can be instantiated by your code or controls as an object data source.
What have I found?
Pure Linq is not always possible on big applications or projects (so you will end up with many things in linq and some in previous more simple solutions to access your repositories) but will help you to save time.
Implementing stored procedures is a MUST if you want to deliver great quality applications.
Hope this comment helps.
Cheers.
I'm going to start a new project which is going to be small initially but may grow to big over the years. I'm strongly convinced that I'm going to use ASP.NET MVC with jQuery for UI. I want to go for MySQL as database for some reasons but worried on few things.
I'm totally new to Linq but it seems that it is easier to use once you are familiar with it.
First thing is that accessing data should be easy. So I thought I should use MySQL to Linq but somewhere I read that it is not directly supported but MySQL .NET connector adds support for EntityFramework. I don't know what are the pros and cons of it. DbLinq is what I also heard. I would love if I can implement repository pattern as it allows to apply filter in logic layer rather than in data access layer. Will it be possible if I use Entity Framework?
I'm also concerned about the performance. Someone told me that if we use Entity framework it fetches lot of data and then filter it. Is that right?
So questions basically are -
Is MySQL to Linq possible? If yes where can I get more details on it?
Pros and cons of using EntityFramework or DbLinq with MySQL?
Will it be easy to access data using EntityFramework or DbLinq with MySQL?
Will I be able to implement repository pattern which allows applying filter in logic layer rather than data access layer (when I use EntityFramework with MySQL)
Does it fetches hell lot of data from database and then apply filter on it?
If it sounds too many questions from my side in that case, if you can just let me know what you will do (with a considerable reason) in this situation as an experienced person in this area, that should answer my question.
As I am fan of ALT.NET I would recomend you to use NHibernate for your project instead of EntityFramework, you may google for the advantages over it, I am convinced you'll choose it.
Based on the points you've mentioned, then I would seriously consider going with MS SQL instead of MySQL initially and implementing LINQ-to-SQL instead of Entity Framework, and here's why:
The fact that you are anticipating a lot of traffic initially tells me that you need to think about where you plan to end up, rather than where to start. I have considerably more experience with MS SQL than I do with MySQL, but if you're talking about starting with the community version of MySQL and upgrading later, you're going to be incurring a significant expense anyway with the Enterprise version.
I have heard there is a version of LINQ that supports MySQL, but, unless things have changed recently, it is still in beta. I am completing an 18-month web-based project that used ASP.NET MVC 1.0, LINQ-to-SQL, JavaScript, jQuery, AJAX, and MS SQL. I implemented the repository pattern, view models, interfaces, unit tests and integration tests using WatiN. The combination of technologies worked very well for me, and I plan to go with the same combination for a personal project I'm developing.
When you get MS SQL with a hosting plan, you typically have the ability to create multiple databases from that single instance. It looks like they give you more storage because they give you multiple MySQL databases, but that's only because the architecture only supports the creation of one database per instance.
I won't use the Entity Framework for my ASP.NET MVC projects, because I wasn't crazy about ADO.NET in the first place. I don't want to have to open a connection, create a command object, populate a parameter collection, issue the execute method, and then iterate through a one-way reader object to get my data. Once you see how LINQ-to-SQL simplifies the process, you won't want to go back either. In the project I mentioned earlier, I have over 60 tables in the database with about 200 foreign key relationships. Because I used LINQ-to-SQL with the repository pattern in my data layer, I was able to build the application using not a single stored procedure. LINQ-to-SQL automatically protects against SQL injection attacks and support optimistic and pessimistic concurrency checking.
I don't know what your project is, but you don't want to get into a situation where you're going to have trouble scaling the application later. Code for the end result, not for the starting point, and you'll save yourself a lot of headaches later.
I am currently reading Pro Asp.Net MVC, and they are building all of their linq2sql entity classes by hand, and mapping them with the linq mapping attributes. However, everyone else I see (from google searches) talking about linq 2 sql seem to be using the visual designer for building all of their entities. Which is the preferred way to build l2s entities, and what are the advantages/disadvantages of each?
The only difference I have noticed so far, is I can't seem to do inheritance mapping when using the visual designer, although MSDN says I should be able to so I might just be missing it in VS 2010's interface. However, I'm not so sure I should use inheritance anyway as that could technically add additional joins when I don't need the sub table data.
As a PS, l2s will not be doing any modification of my schema, I will be generating schema changes manually and then replicating them in linq2sql.
Thanks,
We used the designer all the time. It indeed introduces an added step, every time you make a change to the schema you need to import the table into the designer again, but I think that effrot pales in comparison to the amount of code you need to write if you bypass the desginer.
Also note that the designer creates partial classes, you can create an additional file for the partial class that includes additional implementation details. That way, when the table gets refereshed in the designer, it leaves you additional code alone. We do this to add a lot of helper functions to the classes, and also to provide strictly typed enumerated properties that overlay the primitive integer FK fields.
It's true that inheritance would be very difficult to accomplish well, but I think if you need that sort of data layer, L2S may not be the best solution. I prefer to keep my data layer clean and simple, just using L2S to get the data in and out, and then pu more complicated logic in the business layer. If we really needed to do things like object inheritance in our data layer, I would probably explore a more advanced and complicated technology like EF
We've built our entire application framework backend using L2S. I developed most of the this. I started to use the DBML designer but I quickly realized this was a royal pain. Every schema change required a change to the table(s) in the designers. Plus, the entities created by the designer all get stuffed in a single class file, and didn't have all the functionality I wanted, like support for M2M relationships, and more. So, it didn't take long before I realized I wanted a better way.
I ended up writing my own code generator that generates the L2S entities the way I want them, and it also generates a "lightweight" set of entities that are used in the application layer. These don't have any L2S plumbing. The code generator creates all these entities, and other code, directly from a target database. No more DBML!
This has worked very well for us and our entities are exactly the way we want them, and generated automatically each time our database schema changes.
I am using LINQ2SQL in my current project. I have a quite a lot of tables ~30. When I create my DBML file I change some of the column names etc for readability.
Recently if I made a change to the table in the underlying Database I just deleted and re-added the table in the DBML file, but this is getting tedious. How can I mimic any changes to the database in the DBML file? (e.g. new column, drop column, new default constraint etc).
Out of the box, Linq-to-SQL has no update feature - amazing, but unfortunately true.
There's two tools I know of that get around this:
PLINQO is a set of CodeSmith code generation templates which handle DBML generation and offer lots of extra features (like generating one file per db entity) - including updates!
The Huagati tools offer updates and enforcing naming conventions for DBML and Entity Framework
Marc
I'm not expecting this to be the correct answer, but I thought I'd chime in anyway.
My approach has been to use the drag-n-drop feature for creating the initial DBML file. Then, any changes I make in my DB are also then made, by hand, in either the designer or in the DBML file (as XML) itself. (You can right-click on the DBML file, select Open With, and choose XML editor.) Sometimes it is much easier/faster to work with its XML instead of messing around in the designer.
I would only consider the deleting and re-adding, as you have been doing, if the changes were significant. For adding a new column, however, I'd suggest working directly with the dbml's XML, it's probably faster.
Good luck!
Welcome to the world of tedious! Unless I missed something, you're doing it the right way.
SubSonic looks like an interesting alternative, and boasts
It will also create your database on the fly if you want, altering the schema as you change your object.
As far as free solutions, there are a couple of blunt instruments that mostly move you away from using the O/R Designer: SQLMetal and Damien Guard's T4 templates.
There are multiple commercial solutions available that offer a lot more features.
The question you have to ask yourself is: Am I using the right ORM? LinqToSql has quite a few significant drawbacks, database change handling being only one of them.
Do not use the Visual Studio 2008 LinqToSql O/R Designer
The drawbacks of adopting Linq To Sql
First a bit about the environment:
We use a program called Clearview to manage service relationships with our customers, including call center and field service work. In order to better support clients and our field technicians we also developed a web site to provide access to the service records in Clearview and reporting. Over time our need to customize the behavior and add new features led to more and more things being tied to this website and it's database.
At this point we're dealing with things like a Company being defined partly in the Clearview database and partly in the website database. For good measure we're also starting to tie the scripting for our phone system into the same website, which will require talking to the phone system's own database as well.
All of this is set up and working... BUT we don't have a good data layer to work with it all. We moved to Linq to SQL and now have two DBMLs that we can use, along with some custom classes I wrote before I'd ever heard of Linq, along with some of the old style ADO datasets. So yeah, basically things are a mess.
What I want is a data layer that provides a single front end for our applications, and on the back end manages everything into the correct database.
I had heard something about Entity Framework allowing classes to be built from multiple sources, but it turns out there can only be one database. So the question is, how could I proceed with this?
I'm currently thinking of getting the Linq To SQL classes all set for each database, then manually writing Linq compatible front ends that tie those together. Seems like a lot of work, and given Linq's limitations (such as not being able to refresh) I'm not sure it's a good idea.
Could I do something with Entity Framework that would turn out better? Should I look into another tool? Am I crazy?
The Entity Framework does give a certain measure of database independence, insofar as you can build an entity model from one database, and then connect it to a different database by using a different entity connect string. However, as you say, it's still just one database, and, moreover, it's limited to databases which support the Entity Framework. Many do, but not all of them. You could use multiple entity models within a single application in order to combine multiple databases using the Entity Framework. There is some information on this on the ADO.NET team blog. However, the Entity Framework support for doing this is, at best, in an early stage.
My approach to this problem is to abstract my use of the Entity Framework behind the Repository pattern. The most immediate benefit of this, for me, is to make unit testing very simple; instead of trying to mock my Entity model, I simply substitute a mock repository which returns IQueryables. But the same pattern is also really good for combining multiple data sources, or data sources for which there is no Entity Framework provider, such as a non-data-services-aware Web service.
So I'm not going to say, "Don't use the Entity Framework." I like it, and use it, myself. In view of recent news from Microsoft, I believe it is a better choice than LINQ to SQL. But it will not, by itself, solve the problem you describe. Use the Repository pattern.
if you want to use tools like Linq2SQl or EF and don't want to have to manage multiple DBMLS (or whaetever its called in EF or other tools), you could create views in your website database, that reference back to the ClearView or Phone system's DB.
This allows you to decouple your web site from their database structure. I believe Linq2Sql and EF can use a view as the source for an Entity. If they can't look at nHibernate.
This will also let you have composite entities that are pulled from the various data sources. There are some limitations updating views in SQL Server; however, you can define your own Instead of trigger(s) on the view which can then do the actual insert update delete statements.
L2S works with views, perfectly, in my project. You only need to make a small trick:
1. Add a secondary DB table to the current DB as a view.
2. In Designer, add a primary key attribute to a id field on the view.
3. Only now, add an association to whatever other table you want in the original DB.
Now, you might see the view available for the navigation.