I create persistence ignorant classes for an existing DB which is very big and i don't want to create all classes in the beginning i want to create only classes i need and create each class when i need it.
Is there any feature in Entity Framework can do this?
You can build incrementally your EDMX file adding only entities you need to use at the moment. Than you need to define only POCO classes defined in your EDMX file or you can use POCO template which will generate POCO classes for you.
Related
I'm following the EF Code-First approach in a project that works against an existing database, to which I'm adding tables as needed.
This database has a number of tables for which I need to generate POCO classes for, and so I was wondering if there was a straight-forward, clean approach, to generating simple POCO classes from the database ... from which I can continue to work with using the general Code-First paradigm?
You can use the Entity Framework Power Tools for that.
If you want just the simple Poco classes without any relations use this T4 template
Generate entity class from database table
This may seem like a silly question, but I thought I'd ask it anyway :)
When you use Entity Framework's Database First approach you can create an Entity Data Model to describe the structure of your business objects.
You can also use the ADO.Net DbContext Generator to create persistance ignorance POCO classes. However, when you make a change to the Data Model, ie add a new property to an existing Entity, in order for the corresponding POCO class to also reflect this change, do you have to:
Manually add the new property to the POCO class
Recreate all the POCOs again using the DbContext Generator
I guess what I am asking is there anyway the POCO can be automatically updated if a change is made to the Model?
Thanks everyone.
If you're using the T4 Templates that look at the edmx file, you can just regenerate the pocos by running the templates: Click the Transform Templates icon in the Solution Explorer?
)or have I missed something)
I used Ado.net Entity Object Generator template to generate the business objects from the Edmx file. By default it is adding two files namely
Model.tt
Model.Context.tt
The Model.tt template is generating the business objects, can any one explain the use of Model.Context.tt?
Model.Context.tt generates your derived context exposing all ObjectSets, function imports etc. You can further extend this context in your own partial class and add custom methods you need. ObjectContext is entry point to EF functionality.
I was wondering if can change the edmx.cs file (change inheritance and base constructors of object context derived class).
when I try this , all changes will defect as i build the project.
Note I mean changing the object context derived class not entity classes.
thank you.
If you can afford it (meaning if your project is not too complex already), I could suggest that you switch to code-first style (EF 4.1). That allows you to build all the inheritance you want in your objects. And since you create your own context by inheriting DbContext, you also have total flexibility there.
You can use your EDMX (with the T4 template packed in EF 4.1) or your existing database to create the classes (so at least what you have done until today still stands).
http://thedatafarm.com/blog/data-access/quick-look-at-reverse-engineer-db-into-code-first-classes/
http://devlinliles.com/post/Reverse-Engineer-Code-Firste28093Jump-start-for-existing-Databases.aspx
The partial class solution would maybe do it too (depending on what you wish to achieve).
To change in entity frame work class its better to create Shared classes with same name and add your own methods and properties
I've tried to use Entity Framework 4 and POCO for my MVC 3 project. May be, I don't understand the main idea of this ORM, but the problem is following:
I added ADO .NET Entity Data Model and make model according to database.
I clicked Add Code Generation Item and added ADO .NET POCO Entity Generator.
It makes classes for every database table.
I want to add some methods to work with data (Add, Update, Delete, GetAll etc) to appropriate models.
For LINQTOSQL I added partial classes and placed them to Models. But now I can't do it because:
a) Models folder has classes with the same names, which was created by POCO.
b) If I place my partial class in the another folder, it will be another namespace - so, such classes won't be partial one.
c) If I place my code in POCO classes, it can be destroyed during update POCO.
How can I use it? Where sould I place my methods for data working?
Is the best way to make for POCO and EF the other project - http://blogs.msdn.com/b/adonet/archive/2010/01/25/walkthrough-poco-template-for-the-entity-framework.aspx?
First of all you don't have to write your CRUD inside POCO,
There are many places where you can do it like in edmx.cs file or write one more layer which is called as CRUD Services which handles the Database operations using context object.
Now coming to your questions,
Create separate Models folder and place the Model classes in there.
Your Model class may like this,
EmployeeDepartmentModel
{
prop EmpList List(Emp);
prop DeptList List(Dept);
//Emp and Dept are my POCOs
}
So now I have to fill both of these list(Your CRUD question),
For that, I will Create one method in Controller class(its better to write such logic in some another library, but for time being I suggest you to create in Controller),
FillTheModel()
{
EmployeeDepartmentModel.EmpList = EDMX.GetAllEmployees;
EmployeeDepartmentModel.DeptList = EDMX.GetAllDepartments;
}
Now you can bind this model with your view.
You can place the partial classes in another folder and modify the namespace.
I agree with allisewell, but if you really want to add parts to partial classes, give files another name,
e.g. MyPoco.Part2.cs or modify t4 template to name generated files
e.g. Poco.Generated.cs