I read previous post "Can I use the latest features in Oracle Developer Tools 11g and still use ODP.NET version 10.x or 9.x in my application?".
In this the solution was:
"Solution: Yes, you can use the newest 11g version of Oracle Developer Tools while developing code that relies on ODP.NET version 10g or 9i. In almost all cases it will work fine. The only exception is with the automatic .NET code generation feature. Here is what you need to do:
a) Install both ODT 11g *and* ODP.NET 10g or 9i. They must be placed in different Oracle Homes!
b) You will now be able to use the 11g Oracle Developer Tools for Visual Studio and all of the newest features. To ensure the correct version of ODP.NET is used by your application continue to the next steps:
c) Make sure that in the "References" section in your solution, the Oracle.DataAccess.dll that is referenced is coming from the Oracle 10 or Oracle 9 Oracle home.
d) Finally, you must "ungac" (gacutil /u) the ODP.NET 11g policy DLL's or else your application will silently begin using the 11g version of ODP.NET even though the reference points to the correct DLL. There are several Oracle policy DLLs with varying names, for example: "Policy.2.102.Oracle.DataAccess.dll". Ungac them all."
Are the steps the same if i have Oracle Developer Tools 12c and still use ODP.NET version 11g R2 in my application?
Yes, this is still true.. again with the caveat of code generation issues (which includes Entity Framework).