问题
I am nearly sure this was available and working before, but at this site I have a very recent upgrade from VS2010 to VS2012. I find that if I double click an .edmx file, it by default opens in an XML editor. Also, the Enterprise Data Model item template is missing, so I must open the project in VS2010 just to add a new data model. Are there any known issues that could cause this?
回答1:
you have to select the Microsoft Web Developer Tools in the VS2012 setup to get EF back. Now I have the designer.
// Edit Selecting Microsoft SQL Server Data Tools also installs the EF Designer:
回答2:
I'm able to open EF items. Note that I had installed Entity Framework using Nuget Package Manager earlier. I am able to see a lot of Item Templates in the 'C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\ItemTemplates\CSharp\Data' Directory.
Is that present on the system where you are having the trouble?
来源：https://stackoverflow.com/questions/12726586/edmx-designer-and-item-template-missing-from-vs2012