I'm using VS 2013 and SQL Svr 2012 and trying use EF to populate a gridview. As this is a very simple test, I have just one table with a key and a couple of data fields. The process of creating the model seems to work fine - it shows as expected in the designer view, the files are created in app_code, a bin folder is created with 2 dlls, and the config file is updated with a connection string and other entries.
When I try to select the "named connection" I get the error "Unable to load the specified metadata resource" and it talks about rebuilding the project to get the assemblies.
I've spent hours reading other cases like this and I can't understand:
Why this is happening when it was never a problem with VS 2010
How do I fix the connection string to point to the resources it wants. I'm totally lost with all the technical advice about fully qualified assembly names - nothing I try works.
How do I set some parameter to force the resources to be in the proper place? All the advice I've read doesn't seem to relate very well with VS 2013
I need to decide if I should just uninstall VS 2013 and use VS 2012. Currently, I'm using VS 2010 with ASP 4.0 and I'd like to move to ASP 4.5 and generally keep up with Microsoft technology. However, I don't have the skill level to deal with a VS release that is buggy. It seems to me that this EF execise could be due to a either a bug or some odd corruption on my computer - I'm trying to figure out which is the case. I installed VS 2013 Express and SQL Svr 2012 on a clean machine that had none of these tools in the past.
I'd really like to see someone who is very familiar with Visual Studio try to replicate my problem as it only takes a few minutes to do so:
In MS SQL Server, create a tiny DB with one table that has a primary key and a couple of data fields and populate with some test data - Call it TinyDB with TestTable1.
Using VS 2013 Express for Web, create an "New Web Site" with the option for "ASP Empty Web Site" using VB.
Add an ASP App_Code Folder containing an "ADO.Net Entity Data Model" and leave the name as "Model".
Generate the model from the DB and make a "New Connection" for "TinyDB" and using Entity Framework 6.0 and then select "TestTable1". Note the namespace is "TinyDBModel". Clicking "Finish" will generate several items in App_Code, other folders and also update web.config.
Add a web form called default.aspx and drag a gridview onto it. In design mode for the gridview, select "new data source" and then the "Entity" option (note name of EntityDataSource1 which appears in default.aspx). Click next and under "named connection" select "TinyDBEntities" - this is where mine gets the error "Unable to load the specified metadata resource".
Note that this exact exercise in VS 2010 works perfectly and produces a grid with the correct data displayed.
Unfortunately, the EntityDataSource control does not work with the latest version of Entity Framework, EF6. Hopefully the control gets an update in a future update version of VS or EF, but for now you can't use the two together.
There are a few solutions / alternatives:
Drop back to EF 5. In order to do this, delete the .edmx and .tt files from the App_Code folder, delete the EF assemblies from the Bin folder, and remove the references to EF from web.config. Then rebuild the site, add a new ADO.NET Entity Model and choose version 5 in the Choose Your Version dialog. Then delete the .tt files from the App_Code folder, open the EDMX diagam, right-click an empty spot and on the Properties Grid set Code Generation Strategy to Legacy ObjectContext. Then rebuild again, and it should work.
Use Model Binding. This is really the recommended solution. The Microsoft / EF team recommends people to stay away from the EntityDataSource control and only use it for Dynamic Data web sites, Model Binding is the preferred solultion. It's pretty clean and straight forward to use, and gives you a lot of control over your queries and object updates. For more info about Model Binding, check out: http://www.asp.net/web-forms/tutorials/data-access/model-binding/retrieving-data
来源：https://stackoverflow.com/questions/19609609/visual-studio-2013-and-entity-framework