The ADO.NET provider with invariant name 'Npgsql' is either not registered in the machine or application config file, or could not be loaded. See the inner exception for details.

[bogdandynamic]

Just installed the .vsix extension (from release 3.2.0) into VS 2015 Community Edition, created a WinForms project targeting .NET Framework 4.6.1, added from Nuget the EntityFramework 6.1.3, Npgsql 3.2.0, EntityFramework6.Npgsql 3.1.1, built the solution. Everything is ok until now. But when I try to run the project, mainly when executing a LINQ command of a context object (getting a count of rows from a table) the exception appears:

The ADO.NET provider with invariant name 'Npgsql' is either not registered in the machine or application config file, or could not be loaded. See the inner exception for details.

As you said in the documentation, it is no more necessary to include DbProviderFactory entry in app.config or in machine.config or register the assembly to GAC. What am I doing wrong ?

[bogdandynamic]

When adding

<system.data>
  <DbProviderFactories>
      <remove invariant="Npgsql"/>
      <add name="Npgsql Data Provider" invariant="Npgsql" description=".Net Data Provider for PostgreSQL" type="Npgsql.NpgsqlFactory, Npgsql, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" support="FF"/>
  </DbProviderFactories>
</system.data>

to app.config, everything works fine.

[roji]

This is the expected behavior.

If you use the ADO.NET DbProviderFactory API, the Npgsql provider must be registered in your application's App.config (or in your machine-wide machines.config in some specific scenarios). This is something you must do at the level of your project - the VSIX only takes care of PostgreSQL support within Visual Studio itself. To better understand this distinction, imagine someone else cloning your project from git; they're not necessarily going to have the Npgsql VSIX installed, but your App.config is checked into your source control so will automatically be there.

I'll add a note in the documentation making this clear.

[yikekas]

uninstalling and reinstalling Npgsql.vsix resolved this problem for me.