I have a pre-existing database and Entity Framework 6 database-first model generated from it. I need to create the same database on a different host and/or database engine. I hoped I could use the same model as code-first, but OnModelCreating method of the generated DbContext seems to be protected from being used for code-first approach, it throws UnintentionalCodeFirstException. Generated models don't have any attributes applied too.
Is there any way to reuse my database-first model to create a database with the same schema? Or maybe there's an obvious and much simpler way to do it that I'm missing?
If you just want to create the database you shouldn't need to touch the OnModelCreating method. You should be able to do this from the designer (right click on the designer surface and select "Generate Database From Model" and run the script) or if you want to do this from code do ctx.Database.Create() or use the CreateDatabaseIfNotExists initializer.
Related
I am new to Entity Framework. I have created an EF Model and successfully added some tables and relation. Then I Clicked Generate Database from Model and My DB has been updated. Then I renamed some columns and I don't know how to revert or apply the changes. And Update Model from database does not seems to work because the columns names are different yet.
I need to graphically sync DB with Model. I prefer the model data rather than db data.
Thanks in advance.
You might want to look into the Code-First approach of Entity Framework. Using that approach you'll define your model in your code, and when changing anything you can create a Migration which allows you to up- and down-grade the DB to a specific version from the package manager console (or just create the respective SQL scripts).
For more information on this subject please see this article on MSDN
Note that you can also reverse engineer the code first model from an existing database (see 3. Reverse Engineer Model in this MSDN article), and then enable migrations for that model (see Step 2: Enable Migrations in this MSDN article)
What I do when I make "updates" is do it on both sides manually, in db and then in model (by right click properties) if the change is small. If adding a "new" table I drag it over to model from db server connections panel.
The alternative I've seen others prefer to use in this cases is to stay away from Entity Framework and use Dapper where you pass queries to it and it handles the rest.
Dapper (Wins!) vs Entity Framework vs ADO.NET Performance Benchmarking
I have 20 class.cs with x00s properties for my old project
and now i want to use EntityFramework
but I dont want to rewrite all this classes from begin
i just want to convert this class to DataModel.dbml or use some thing like add Existing Item
and I tried creat class with same name and copy the code inside them but the editor clear them after saving
how can i do that ?
There is plenty of resources regarding Plain Old CLR Objects and Entity Framework code first model on the web.
ADO.NET EF 4.0: Working with Plain Old CLR Objects (POCO) Classes
Code First step by step tutorial
But the gist of it is:
Entity Framework >4.0 supports POCO types that don’t need to inherit from a base class or
implement any interfaces to get persistence. There is also no need for metadata or mapping
attributes on type members, so you can use your existing code as simple entity classes.
An EDMX file that contains the conceptual model is still required. Add a new ADO.NET Entity Data Model to the project.
Using the toolbox, drag entities and associations from the toolbox and design the conceptual model. Simply make sure that the names on your POCO classes match the names of your conceptual entities.
Add entity keys as you would add primary keys in a db. Add associations like foreign keys in a db.
In Solution Explorer, click the EDMX file and then, in the Properties window, clear the Custom Tool property to turn off the automatic generation of .NET classes for your conceptual model.
Right click edmx design area and select 'Generate database from model'. DDL will be produced. Run that to create your db.
Make sure your POCO classes and POCO edmx model are in a separate assembly.
Create your custom ObjectContext derived data context with ObjectSet<T> members like here. Newer EF releases use System.Data.Entity.DbContext and System.Data.Entity.DbSet<T> instead.
You can use dbml too (Linq To Sql classes instead of EF), but you still need to generate your model from scratch, like you'd do with EF.
Assumptions
Using EF 6.1, MVC 5, VS 2013, C#
I have an existing database model designed in Toad DM for SQL Server and it's very important keep it always updated
Steps and Notes
Using ADO.NET Entity Data Model I chose Code First from Database (new feature in EF 6.1) to generate the models. Note: Model classes and DbContext class generated successfuly but NO .edmx or .tt file was generated.
Next I added a new scaffold item: MVC 5 Controllers with views, using Entity Framework. Note: Success, controllers and views generated
Question
From now on I don't want to use Code First to update my database. Instead I want the models to be updated based on database changes. What to do next? If I don't have an edmx file will I not be able to update my model classes from the database?
The Entity Data Model Wizard's Code First from Database does an excellent job creating your entity classes, as if they were created in the Code First style. What you are asking is if there is any way to keep these classes up-to-date as your database changes, similar to the EDMX style "Update Model From Database". From what I've researched this is not possible using the built-in tooling. However, here is one workaround that I've found useful:
Let's say I have database with a product table and customer table. Originally I created a StoreDBContext class, and selected product as one of my objects. Now I want to add the customer table as a new entity to the existing context. Here's how to do this using the Code First Wizard:
Create a new Entity Data Model, call it StoreDBContextTemp or whatever
Choose the code first from database wizard option
Select customer as an object to add (just customer) & complete the wizard
Open the newly created context file, StoreDBContextTemp.cs, and copy the virtual properties of your newly added entities:
public virtual DbSet<Customer> Customers {get; set;}
Paste these new properties into your Original StoreDBContext.cs dbcontext class.
Delete StoreDBContextTemp.cs, and remove the connection string for StoreDBContextTemp in app.config/web.confg etc.
You can now use Customer on the StoreDBContext class
If you add or remove tables you will need to manually adjust fields, but at least you won't need to hand write dozens of properties each time a new table is added to the model.
One more option is just delete the auto generated classes from the project and once again generate them.
While following this approach only thing we need to make sure that is we should give the same name for the data model(class name which inherits from DbContext ) as the previous one.Data model name is highlighted in below snap
Three things.
There's no .edmx when you use Code First.
If you use Code First Migrations you would have to write first the code and after that migrate the changes to database. This helps you to have much more organized you code with no generated code which is an advantage.
There's a plugin in Visual Studio for doing contrary. Entity Framework PowerTools allows you to select the database and map it to objects.
https://visualstudiogallery.msdn.microsoft.com/72a60b14-1581-4b9b-89f2-846072eff19d
The best solution to me is deleting the model and recreate updated one with the same name, keeping in mind two points:
Personal extension methods implemented for the model;
Possible manual relationships between tables added to the model because of not setted up in the phisical db.
My personal solution:
Move all extension methods to another partial class that won't be overrided;
Insert all added properties of an entity to another partial class;
Keep track of all manual relationships in an help file, so you can add them again being sure not to loose anything;
Delete the old model and recreate one new with the same name and update it with the manual relationships of point 3.
I want to convert my code-first project to Database first. Is there an automated way or should I just delete the entities and context code and create a model from the created database?
It appears Entity Framework Power Tools supports a feature called "Reverse Engineer Code-First". You can download it here.
There is no way to convert your code-first classes into database-first classes. Creating the model from the database will create a whole new set of classes, regardless of the presence of your code-first classes.
However, you might not want to delete your code-first classes right away. The entity framework database-first model creates partial classes for all of the entity objects. If you have any business logic (anything besides the plain old properties) in your code-first classes, you can declare them as partial, remove the properties, and maintain the business logic. Essentially, you're letting EF generate the properties in the *Designer.cs file, while you define the business logic in your .cs files.
I have a new project I am starting and I would like to use entity framework 6 code first to handle the database portion. The problem is, I do not have permissions to create a new database on the server I need to use. Because of this, I would like to create a new schema in an existing database and then have entity framework only interact with that specific schema. There are many other tables in other schema in the database that are related to other projects (none of which make use of entity framework in any way) and entity framework needs to leave them alone when it is creating/dropping/modifying tables related to my project.
Is that possible? If so, how do I go about setting that up?
It turns out this is actually pretty easy using EF6! In your context just override OnModelCreating and add
modelBuilder.HasDefaultSchema("schema_name");
before the call to
base.OnModelCreating(modelBuilder);