I am writing my first WPF and EF application. I am using SQL CE database and I have added few tables to the DB. The EF diagram is generated and now I want to generate the classes. I am new to EF and MVVM both.
When I right-click on a Table diagram, it gives option "Add Code Generation Item..". On selecting it, there are two options:
Add Entity Object Generator
Add Self-Tracking Entity Object Generator
I want to know what is the difference between the two. Which one should I use? I also want to know which one is latest and what is POCO?
A POCO is a Plain Old CLR Object... a simple class that has only properties.
http://en.wikipedia.org/wiki/Plain_Old_CLR_Object
There are 3 approaches that the Entity Framework delivers.
Model first (you create a model in visual studio and generate the database)
Database first (thats what you do, you generate a model from a existing database)
Code first (the newest one, you just write you POCOS and the entity framework generates the database)
I think it is enough to generate the diagram from database. The context and models should be available after this.
Neither of those is the POCO generator. The best way to get that is to install Entity Framework 4.1. You'll then see some new options in the list to add a code generation item.
I'm a pretty big fan of the DbContext/POCO generator added in 4.1 as the code it creates is VERY easy to work with compared to the older stuff, and it works well in a DB First setup like you're using (which is also what I use).
You can give this code generator a try:
http://salardbcodegenerator.codeplex.com/
It generates data annotations and implements INotifyPropertyChanged for CodeFirst approach.
Related
I know entity framework designer is used to create the classes of model-first approach and then we create the database by using that class. But in code-first appraoch, it is possible to create the custom classes, within that classes the database is created automatically. Then what is the difference between code-first approach and model-first approach?
Code First is the more modern style of working with Entity Framework. As the name implies, you write the code first and the database model is generated for you, by using Entity Framework Migrations. In this scenario you are not using any graphical tool at all, everything is just pure code.
Model first means creating the abstract database model in the designer. The code is then generated by templates. If you update the model, the code will be regenerated.
I'm following an MSDN article on applying the Repository Pattern and the Unit Of Work Pattern to Entity Framework, but I'm stuck at the mapping between the custom-made domain models and the as-yet-nonexistant database.
The article has me create two simple POCOs, Employee and TimeCard. It also walks through creating generic repositories and custom implementations therein. (I'm using the custom repositories so I can try to keep EF dependencies in the data access assembly.) However, they sort of glaze over an important step in the mapping. The article says:
With the POCOs in place we can create an Entity Data Model (EDM) in Visual Studio (see figure 1). We will not use the EDM to generate code for our entities. Instead, we want to use the entities we lovingly craft by hand. We will only use the EDM to generate our database schema and provide the metadata EF4 needs to map objects into the database.
The "Figure 1" it references is here:
But that's all it says on the subject. There's an aside on how to generate POCOs from an EDMX. There's lots of information via Google on how to generate POCOs, generate EDMX from a database, etc. But in this walk-through we already have the POCOs and I need to use them in the EDMX which would, in turn, generate the database (I'm assuming, based on other code-first walk-throughs).
I've added an "ADO.NET Entity Data Model" to the project, which is basically a blank canvas. But I'm not seeing how to add my existing POCOs to that canvas. Do I have to re-create them manually on the design surface (which would be a pretty significant duplication problem in a larger domain)? If so, how do they map to the existing ones?
Typically when you use the designer the flow is the opposite - you create the model with the designer (or create/update the model from the database) and then the code is created for you. The created code can be either the EF1 style code with entities derived from EntityObject and attributes etc. which is created with a Single File Generator which is a part of VS (Code Generation Strategy set to "Default") or the code can be created with T4 templates (Code Generation Strategy set to "None") in which case you need to add T4 templates to your project. EF matches POCOs with Entities from the edmx file by convention (names of entities have to be the same, names and types of properties have to match etc.). In the article for some reason they went the opposite way which is weird since it requires that you create all the entities and relationships with the designer manually (since the designer does not know how to create entities from the code) and make sure that the requirements for the conventions (you may not even be aware of some of them) are met. However when you start with code the better approach is to use the EF Code First approach and skip the designer entirely. Code First can create database from your code. It also contains migrations feature which allows evolving your database along with your code. Finally (as you seem to use Visual Studio 2010) you could use EF6 which allows using all the goodness that was previously only available on .NET Framework 4.5 to be used on .NET Framework 4. See here for more details: http://entityframework.codeplex.com/
*the names are going to change in the new version designer that supports EF6 and works with Visual Studio 2012 and Visual Studio 2013
EDIT to address questions from the comment
If you would like to use Code First would use the DbContext API which is a streamlined wrapper of the ObjectContext API. Here is a walkthrough that should help get you started.
You can still use Code First if you have an existing database - the difference is that you will not be able to use migrations. The easiest way to get started with this is to use EF Power Tools. Take a look at this tutorial to see how to do that.
More help here
I want to know if there is a way to generate the class dynamically at runtime. I want to use it in Entity framework code first.
Consider if I have 100 tables(or connect to unknown database) I will have to create model/POCO for each table in EF Code First, instead of this I want to generate the POCO class and all its properties at runtime based on the database connected.
Probably not.
Consider this... If the classes aren't defined before compilation, then how is any other code going to use them? If no other code is going to use them, why do you need them?
You can generate objects based on the table schema at design time. Doesn't Entity Framework in fact do this already?
I realize that I've linked to something that is "database first" instead of "code first" but, well, that's what you're asking:
I want to use it in Entity framework code first.
[...]
I will have to create model/POCO for each table in EF
You have a database, and you want to generate models based on the schema of that database. That's database-first.
You can use the EF Power Tools (beta 3) for Visual Studio 2010 or 2012 to reverse engineer a database to POCOs. After installation, right click on a project and select Reverse Engineer Code First under the new Entity Framework menu group.
The Power tools: http://visualstudiogallery.msdn.microsoft.com/72a60b14-1581-4b9b-89f2-846072eff19d
Rowan Miller has a blog post about this, and some advanced uses: http://romiller.com/2012/05/09/customizing-reverse-engineer-code-first-in-the-ef-power-tools/
Is it possible to auto generate the POCO classes and the mapping with the database defined separately using Fluent API (instead of annotations) for an existing database? Instead of coding all these entity classes manually, I find it easier if they are auto generated and then I can change them as required if the names are not incorrect (plural or singular) or the some of the relationships are not correctly mapped etc. This will save lot of time for me compared to coding all the entity classes and relationships from scratch and I am not that familiar with the fluent API syntax as well.
Yes, i encourage you to use Entity Framework Power Tools CTP1
Reverse Engineer Code First - Generates POCO classes, derived DbContext and Code First mapping for an existing database.
hope this helps
The Power tools are incredibly slow to generate files. It takes over an hour to work on my companies database (has a lot of tables).
Instead take a look at this visual studio extension http://visualstudiogallery.msdn.microsoft.com/ee4fcff9-0c4c-4179-afd9-7a2fb90f5838
It generates cleaner code, WCF serialisation classes, and includes the database default constraints as part of the POCO ctor.
Disclaimer: I should mention that I am the author of this extension
We are about to start using EF as our ORM. We have our own MetaData representing the databse stracture and we will generate whatever we need off of that.
We are wondering whether to use the "old" EDMX approace, or to use the new EDMX free approach (wiht DbSet and DbContext). As we do our own code/edmx generation it seems odd to generate an EDMX and then generate objects and context off of it.
The thing is I don't see much talk about about the EDMX free approach. Is it being used by anyone? Can someone with experience share their impressions? Are there known limitations? Are there pros and cons?
Asher
Are you asking if anybody is using code-first? :) By checking the number of questions in entity-framework-4.1 and code-first and ef-code-first I guess people are using it a lot. There were several questions about code-first x non code-first. Some of I answered:
EF POCO code only VS EF POCO with Entity Data Model
EF Model First or Code First Approach?
EF 4.1 Code-first vs Model/Database-first
Generally there are four approaches:
Model first (database generated from EDMX)
Database first (EDMX generated from database)
Code first (database generated from code mapping)
Database first with code mapping (code mapping manually created for existing database or manually updated mapping generated by EF Power Tools CTP)
Selection of the approach usually depends on the way how you want to develop application (as described in linked answers). It also depends if you want to use ObjectContext API or DbContext API. The former one is usually used with first two approaches (but the secret is it should work with code-first as well) the later one with all of them.
Code first has some limitations - it doesn't support all mapping features EDMX does for example:
Stored procedures mapping (it doesn't mean you cannot execute SP when using code first)
SQL functions mapping
Advanced EDMX features like defining queries, query views, model defined functions
etc.
What I don't understand is why are you trying to combine your code generation tool with EF. Either use your stuff or use EF's stuff. You will avoid complications and incompatibilities.