Now that i have generated 19 code-first classes from an existing database by:
Creating a Model-First Entity, and choosing "Generate from database"
Right clicking and choosing "Add Code Generation Item"
EF 4.x DbContext Generater
All the classes i want are generated, and I'm very happy with them...
And now for my question(s)
Why are they all the generated .cs files nested in a sealed .tt collection?
Why can't i copy paste them out to any folder i like, and treat them like normal classes?
Is it just me, or are you unable to use migrations "update-database" when you do it like that?
I guess my overall question is, why are they located in a .tt folder?
And how shall i update my database now? By editing the database manually and then update the Model, and then generate the dbContext again? Or is there a trick to get .cs files out of a .tt folder?
How do you modify you database after generating your DbContext?
Why are they all the generated .cs files nested in a sealed .tt collection?
Your code-first classes are not code-first classes. They were generated based on your database schema. Hence, this is a database-first approach. With database first, your entity classes are generated based on the database. In other words, the database comes first, the code comes second. The .tt file is a T4 template that decides how to generate your classes based on the database. You could change the database and then regenerate your entity classes.
Why can't i copy paste them out to any folder i like, and treat them like normal classes?
Because they are generated files, based on the T4 template.
Is it just me, or are you unable to use migrations "update-database" when you do it like that?
This part of your question I can't answer for certain, and will have to defer. However it seems to me like you want to mix and match approaches. It sounds like you want to start by generating code classes based on your database, and from there forward, change the database based on new entity classes you add to the model project. Is that right?
You can forgo the code-generation part and just go with a pure code-first approach, now that you have an idea of what the entity POCO's should look like. I have tried this T4 code generation before (pre EF 4.1) and immediately abandoned it, because as you have seen, since the entity and DbContext classes are generated, you lose control over the object-oriented model.
Related
Using Entity Framework 6 Code First in an ASP.NET project with Visual Studio 2013, is there any way to rebuild (or update) the generated DataContext and model classes without stepping through the Entity Data Model Wizard every time?
I'm fully aware of how to do this with an EDMX designer, but again, I'm using the "Code First from database" method and just wondering if there's a one-click (or one console command) way to trigger the rebuild without having to delete the generated context class and then step through the Entity Data Model Wizard every time I make a change to the backing database.
In VS 2015 (and supposedly 2013/2012) you can use the Entity Framework Reverse POCO generator to accomplish this.
https://visualstudiogallery.msdn.microsoft.com/ee4fcff9-0c4c-4179-afd9-7a2fb90f5838
You can make all your changes to database first, and to re-generate your models all you have to do is save your Database.tt file (usually I just add white space).
Code first requires you to create the DataContext by hand. You don't create/change the database and refresh the DataContext class. The Code first from database or EF Reverse POCO template is a middle ground between true Code First and the Database First approach of doing things. It meets at the middle by generating the same kind of POCO classes that you would have written by hand in Code First. They don't do it in Code First way but the end result is something similar to Code First. Hence the confusing name.
If you are using one of these templates to generate POCOs, you can right click on the t4 template file and click Run Custom Tool. If that doesn't work, you might want to delete that entity and then run the custom tool again. Also right clicking on the EDMX and clicking 'Update Model from Database' should work.
I have the solution for rebuild without wizard:
using the t4 is Transform All T4 Templates
and create the classes
I'm in the process of converting an extensive EDMX model into POCO classes. I need to go from a Database First approach (EDMX with ObjectContext) to a pure Model First approach (DbContext with no EDMX file). I need to use the latest Entity Framework stable version: 6.1.1.
I've tested some approaches:
Adding a the EF 6.x DbContext Generator code generation item by right-clicking the blank space in EDMX designer. This works fine, but it doesn't add any mappings. With this approach I have to still use the EDMX file. It's not full Code First.
Using the EF 5.x DbContext Fluent Generator for C#. This triggers an exception in design time. I'm not being able to use it. I don't know if that's because my VS Entity Framework tools are already updated to 6.x. Using the alternative TT in the comments, that suggests that it would work with EF 6.0 also doesn't help.
Using the EntityFramework Reverse POCO Generator. This is the worst because it won't consider any of my classes and navigation properties renames.
Using the Entity Framework Power Tools Beta 4. Again, it only supports generating from the database, not from the EDMX file.
My requirements:
I need the input to be the EDMX file, not the database.
I need the output to be a full Code First approach with Fluent mappings.
I need all my navigation property names defined in the EDMX to be considered because otherwise it would break a large codebase, even more then migrating from ObjectContext to DbContext will break.
What do you think would be a good option for me to go?
Well i don't think there is an easy one click solution to this.
Underneath you edmx files. You have two more files available besides the xx.Designer.cs and xx.edmx.diagram.. called xx.Context.tt and xx.tt where xx is the name of your edmx model.
These are t4 templates which genrate your dbcontext and poco objects. All your poco objects would be created underneath your xx.tt files and dbcontext underneath your xx.Context.tt files.
You now have to moves these into separate files. This is much easier if you are using EF6. and the file generated are already using DbContext and not ObjectContext.
I faced a similar case and I used Entities to DTO's generator.
Although its purpose is to generate DTO's, however, I believe it can help someone in you case.
https://entitiestodtos.codeplex.com/
In a class library Ado.net Entity Data Model is has generated POCO classes. These were generated fine for the first time. But database changes are not being reflected. In edmx diagram right clicking and choosing Update Model from Database show newly created table but it do not add table even after selecting it to add.
I tried running .tt (by right click and Run custom tool) but even it did not regenerated the Poco classes as per latest DB changes.
Help please
Not a fix but a workaround: Is it not an option to simply remove and regenerate the EDMX and the generated classes? That's what I do, it is much easier than working with the update feature, and the result seems to be the same. Your POCO extensions still remain the same and functional.
I use database first and I have my SQL upgrade scripts, the generated EDMX and my Generated models in source control and the changes there are very easy to manage. Here is a rough outline of my DB upgrade process for each version:
Create .sql script for the upgrade, statements like CREATE TABLE etc.
Delete generated files: Model.Context.tt, Model.tt, Model.edmx
Remove Entities string from Web.config (if you use it)
Create the EDMX and Context files the same way you did for the first time
If you use source control (I hope you do!) check what has changed
Test
Commit!
In my case i needed to save ModelName.edmx, then classes were generated.
Ensure that connections string in app.config is correct. I was using a DataDictionary and my connection string had the following path:
data source=|DataDirectory|*.sqlite
Thus, it wasn't updating. Because this DataDirectory variable was being resolved at runtime.
I have added added Entity Framework to my project and selected Code first from database when creating my models. But the problem is, i couln't find how find how to update existing models and add new models to my project when i make changes on database.
It is very straightforward. Switch on migrations, change/add you classes, create a migration and update your database. See here for example. There are plenty of other sources.
When you change your DB you can run the EF generation again but it will overwrite the existing files so you will lose any changes. If you want to maintain code outside the generated files then you can use partial classes. Or alternatively just code them by hand after the initial auto generation, it's quick once you get used to it! :)
I have an existing database that I want to generate its POCOs but I want to end up with model classes outside .tt file, without giving partial definition and "auto generated" comment header for each class I want to have a result like I started building POCOs from scratch. Is there a process to get this result ? Regards
I want to regenerate my database and start updating model from POCOs using migrations
Update : After editing Template File (.tt) I could remove the header comment and partial definition. I think I could get my work done manually. Now, I just need to Exclude .tt file and its sub classes from project and then add only my business classes to the project again.
You can use Entity Framework Power Tools Beta 3 extension to generate your pocos. It has an option to reverse Engineer Code First which Generates POCO classes, derived DbContext and Code First mapping for an existing database.