I have read all that I can find, but no luck. In Visual Studio 2015 Community, here is what I did (with no luck):
When I go to add the ADO.NET Entity Data, I check model from the database. Set the connection (it tests good). Upon returning from the connection window, the Wizard closes immediately.
How are the newest versions of EntityFramework6 and Npgsql installed for ADO.NET?
Everything is described here, step by step on the page. Below is a link to github: How to setup NpgsqlDdexProvider 3.1.
I use Visual Studio 2015 and the database server PostgreSql 9.4. I installed Npgsql-3.1.8.msi who installed library Npgsql.dll in the GAC:
and installed NpgsqlDdexProvider-3.1.0.vsix that allows you to add a connection string under VS in Server Explorer for PostgreSQL.
It's work perfectly for me.