I'm trying the database first approach by creating an ADO.NET Entity Data Model using the wizard with the Adventureworks2012 DB.
Testing DB connection works, and the connection string is added to the App.Config.
I'm selecting all the tables except the ones marked as (dbo) AWBuildVersion, DatabaseLog, and ErrorLog.
When the wizard finishes the .edmx file is blank, and if I view the file in XML view the EntityContainer is empty.
After the model is created it returns this error in the output window:
Unable to generate the model because of the following exception: 'The
table AdventureWorks2012.Production.Document is referenced by a
relationship, but cannot be found.
I'm using VS 2010 & .NET Framework 4.0
It seems that Entity Framework does not know how to deal with data types like hierarchyid set on a table field. I removed the Production.Document table for the list of entities to include solving my problem.
Note also that this reference below was for Adventureworks 2008R2 with EF version 1.0 from Code Plex SQL Sever, and I am using Adventureworks 2012 from the same CodePlex site using EF version 4.4.
Reference: http://msftdbprodsamples.codeplex.com/wikipage?title=AW2008Details
Note: EF 1.0 Compatibility Issues
The Entity Framework team would like us to let you know that AdventureWorks2008 is a little bit ahead of the curve in terms of the Katmai features it uses. Some datatypes in AdventureWorks2008 (such as hierarchyid and geometry) are not supported in the entity framework. The workaround is to exclude tables like Production.Document from your model if possible since there is currently no support for the hierarchyid datatype in Entity Framework 1.0. Unfortunately the Entity Framework tooling which updates your model from the database will pull in tables like Production.Document even if they were specifically excluded when the model was created, so use of that feature on AdventureWorks2008R2 is not supported at this time. We look forward to a follow-on release of Entity Framework which has full SQL Server 2008 type support.
Last edited May 25, 2010 at 2:22 PM by bonniefe, version 17
There is a way to get around this IF you're trying to learn from this example and not doing anything meaningful. I deleted the foreign keys to the offending table and removed it and was able to succesfully get
Uncheck [Allow Nulls] Check-boxes (in the table design) for all the foreign keys of the not created Tables (Tables not converted to the model).
Then you can update your model to retrieve those tables by doing the following steps:-
Step 1 - Right click some where in your .EDMX file's design (i.e. Model1.EDMX [Diagram1].
Step 2 - then from the Context Menu select / Update Model from Database....
Step 3 - then select "Add"
Step 4 - then expend "Tables" Check-Boxes and select your desired tables (tables not created first time).
Step 5 - then click Finish button.
Step 6 - Save the the solution and hope everything will be Ok.
Note: I'm using Visual Studio 2013.
Good luck.
Related
Using Visual Studio 2015 with SQL Server 2012. I've been happily using code first existing database to generate my data layer with no problems, until last week. For some inexplicable reason VS will not generate the Entity classes from my database tables (any solution, any projects, different databases and SQL instances).
The DbContext inheriting model class is generated containing the public DbSet properties for each table, also the OnModelCreating method which contains an entity<>.Property assignment for each field in each table.
Basically VS can talk to the database, read the schema, map and create everything except the entity classes. I am working on Win Server 2008R2 and applied a number of updates prior to the issue. I have since removed the updates, uninstalled then reinstalled VS but to no avail. Searching the web does not highlight anyone else who has encountered this. Can anyone help please? (VS 2013 is working fine).
I have been using Database First Entity Framework (EDMX) and SQL Server Data Tools Database Projects in combination very successfully - change the schema in the database and 'Update Model from Database' to get them into the EDMX. I see though that Entity Framework 7 will be dropping the EDMX format and I am looking for a new process that will allow me to use Code First in Combination with Database Projects.
Lots of my existing development and deployment processes rely on having a database project that contains the schema. This goes in source control is deployed along with the code and is used to update the production database complete with data migration using pre and post deployment scripts. I would be reluctant to drop it.
I would be keen to split one big EDMX into many smaller models as part of this work. This will mean multiple Code First models referencing the same database.
Assuming that I have an existing database and a database project to go with it - I am thinking that I would start by using the following wizard to create an initial set of entity and context classes - I would do this for each of the models.
Add | New Item... | Visual C# Items | Data | ADO.NET Entity Data Model | Code first from database
My problem is - where do I go from there? How do I handle schema changes? As long as I can get the database schema updated, I can use a schema compare operation to get the changes into the project.
These are the options that I am considering.
Make changes in the database and use the wizard from above to regenerate. I guess that I would need to keep any modifications to the entity and/or context classes in partial classes so that they do not get overwritten. Automating this with a list of tables etc to include would be handy. Powershell or T4 Templates maybe? SqlSharpener (suggested by Keith in comments) looks like it might help here. I would also look at disabling all but the checks for database existence and schema compatibility here, as suggested by Steve Green in the comments.
Make changes in code and use migrations to get these changes applied to the database. From what I understand, not having models map cleanly to database schemas (mine don't) might pose problems. I also see some complaints on the net that migrations do not cover all database object types - this was also my experience when I played around with Code First a while back - unique constraints I think were not covered. Has this improved in Entity Framework 7?
Make changes in the database and then use migrations as a kind of comparison between code and the database. See what the differences are and adjust the code to suit. Keep going until there are no differences.
Make changes manually in both code and the database. Obviously, this is not very appealing.
Which of these would be best? Is there anything that I would need to know before trying to implement it? Are there any other, better options?
So the path that we ended up taking was to create some T4 templates that generate both a DbContext and our entities. We provide the entity T4 a list of tables from which to generate entities and have a syntax to indicate that the entity based on one table should inherit from the entity based on another. Custom code goes in partial classes. So our solution looks most like my option 1 from above.
Also, we started out generating fluent configuration in OnModelCreating in the DbContext but have swapped to using attributes on the Entities (where attributes exist - HasPrecision was one that we had to use fluent configuration for). We found that it is more concise and easier to locate the configuration for a property when it is right there decorating that property.
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/
This question already has an answer here:
AdventureWorks can't create ado.net entity data model
(1 answer)
Closed 8 years ago.
I've tried following some simple tutorials to get started with Entity Framework using the AdventureWorks databse. I'ved tried this several times and I get the same results.
Create a Class Library
Add an ADO.NET Entity Data Model
Choose Generate from Database
Create a connection to the AdventureWorks DB
Choose all the Tables and Views
Results: Generates a Blank EDMX that tells me to drag items from the Model Browser.
When I look at the Model Browser, there is nothing there to drag to the EDMX.
Any ideas what I can try?
Using SQLServer 2012 Express
Visual Studio 2012 Express (.NET 4.5)
I was having the same issue.
My table was lacking a primary key.
Adding one did the trick for me : the table appeared in the .edmx
I am developing an EF - MVC 3 application. I have used model first approach, so I have create model first and from that model, EF generated the DB.
I have used a tool called Nuget - Entity Generator - Database designer for generating the database. When I have designed the model first time, I have used the Generate Migration T-SQL and Deploy option of that tool.
Database generated perfectly and it's working fine...
Now I have come across a situation that I have to make a change to the model and I have to use T-SQL Via T4 (TPH) option to update the database.
So previously I used different process to update DB and now I am changing it.
When I use the T-SQL Via T4 (TPH) all the tables get deleted and new tables get created.
How to avoid this ?
I want to only update the table which I have made the changes.
Entity framework 4.3 comes with migration support. This is not available in EF 4.1.
Some links from google:
http://blogs.msdn.com/b/adonet/archive/2012/02/09/ef-4-3-automatic-migrations-walkthrough.aspx
http://blogs.msdn.com/b/adonet/archive/2012/02/09/ef-4-3-code-based-migrations-walkthrough.aspx