I'm new to the Entity Framework. I've created a model-first schema in Visual Studio 2012 with EF5, but I'm having trouble getting the generated code to build. One of my entities ("Test") has the same name as the model (edmx) and the project (csproj) files, so it conflicts with the namespace (Test is a namespace but is used like a type). So I decided to change the namespace by setting a "Custom Tool Namespace" for the .tt files. This worked, but then I found that the "Test" entity's generated .cs file was entirely empty (other entities were generating properly), so I had build errors where other entities reference "Test". Renaming the entity results in a properly generated class, and therefore a building project, but I really want to use the original name.
I will probably end up scratching the project and starting over, ensuring to choose unique names for the project, the model, and the entity. But I'd rather know how to fix this if possible in case I run into something similar when the project is further along and it's not so easy to start over.
you can use use an alias on the Using Directive, e.g. using Project = PC.MyCompany.Project; to differentiate between namespaces. see MSDN
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I've just noticed how terribly tough Entity Framework makes simple task of changing name of some field in some table in the model. There are following difficulties. Renaming (or changing type) of field using GUI:
doesn't change the mapping
doesn't rename names in generated models, but regenerates them
So after renaming a field we need to manually update edmx's xml and deal with all references to old name of the generated POCO in all places of our project.
Is there any way to do it smarter? Are there any tools for it?
(I'm using EF 4)
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
My Solution consists of a different projects. I have a project for each of the contexts and project for a Base Context that all other context classes inherit for only referencing 1 database.
I have 3 other projects for the different Domain Classes(Customer, Rental, Owner) that have the actual entities. Also I have 1 helper class that the Domain Classes have reference too.
My problem is when I right click on any of the context classes and select Entity Framework>View Entity Data Model(Read Only) I get the "Sequence contains no matching element".
Now I have seen a couple of posts about this being a issue if the project actually was within a Solution Folder and as soon as this has been placed on the Solution root it starts working. In my case it is a project on the root directory of the Solution. This is my first project using Entity Framework, so if I am being vague I apologize, I have not seen any solution for my problem so any help would be appreciated.
I wrestled with this today as well. I also have separate projects for the domain objects (entities) and the EF model under solution folders. I finally got it working by first moving the project that contains the DbContext derived class and all its dependent projects out of the solution folder into the root.
Secondly, I needed to drop the default database that EF uses to create the model and it's metadata. It seems that when the power tool runs, it uses the default constructor of the class deriving from DbContext. In my case, that model was way out of date. I typically use an explicit connection string, so the default model hadn't been updated in a while. By default, EF will create a DB on the .\SQLEXPRESS instance, naming the DB after the class derived from DbContext.
Hope this helps,
Jeff.
It may be as simple as having the SetInitializer on database being set to null, and EF needing to upgrade your DB.
Either in code:
Database.SetInitializer<TContext>(null);
or in config
<appSettings>
<add key="DatabaseInitializerForType Namespace.Class, Assembly" value="Disabled" />
</appSettings>
Obviously the config is an assembly reference, the important bit is the 'value="Disabled"~.
This is normal practice so that EF doesn't accidentally drop your database when starting your app.
I created Model1.edmx file and accordingly Model1.Designer.cs was also created.
I decided to copy all code from Model1.Designer.cs to dal.cs file and deleted Model1.edmx + Model1.Designer.cs files.
When I try to connect I get error that mapping is failed and no SSDL,CSDL are found.
Is there any way to use Linq To Entites without .edmx file, but just using the code in Model1.Designer.cs?
If you define your mapping in EDMX there is no way to use it without EDMX. EDMX is necessary because the build process will decompose the EDMX files into multiple resources specifying mapping between classes and database. These resources are used at runtime.
If you don't want to have EDMX file you can't use it at all and instead you can try code first approach (more tutorials are available on that page) in Entity Framework 4.1. You can also use helper EF Power Tools to generate code mapping from existing database for you (it can be good to start learning how to map tables from code).
I work with EF 4 (not with Self-tracking entities currently). I've added some columns (non of them is a key and all of the are nullable) to one of my entities, and got the Number of members in conceptual type does not match with number of members on object side type exception.
I've followed the accepted answer here but all I got from that was that this entity does not appear in my edmx anymore. I've re-added it from DB, but I keep getting the same exception.
I think the problem is that I've copied the csdl/ssdl/msl files to my executing assembly directory. I'd like to copy the updated files, but they're not created again (they were once created in the obj\Debug\edmxResourcesToEmbed folder of my EF project), not even after removing them.
Any way to get those files created again?
Thanks.
P.S: As I don't want to publish excess amounts of code, I don't add anything yet but I'll be happy to add needed information, I'm just not sure what exactly is needed.
So if you want to create the csdl, ssdl amd msl files, do the following:
Go to your edmx file.
Click on the GuI screen that shows the model.
Switch to the property window (I didn't know that it needs to be accessed from the GUI area and not by right clicking the file in the Solution Explorer.
In the Metadata Artifact Process select Embed in Output Assembly.
Done and done, the files will appear in Debug\edmxResourcesToEmbed under obj or obj\x86, depends on your build definitions.
I'm sorry if this seems to simple to explain, but I was in need for those instructions (msdn was not a great help) and I hope it might help others.