How to add custom DB provider to be accessible in Visual Studio?

I wanted to work with custom DB provider in Visual Stud开发者_JAVA技巧io. I need it to use Entity Framework.

For example, I downloaded NpgSQL, registered them in GAC:

gacutil  -i  c:\temp\npgsql.dll
gacutil  -i  c:\temp\mono.security.dll

and added to machine.config file:

<add name="Npgsql Data Provider"
invariant="Npgsql"  support="FF"
description=".Net Framework Data Provider for Postgresql Server"
type="Npgsql.NpgsqlFactory, Npgsql, Version=2.0.6.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />

But Npgsql did not appear in Datasource list in Visual Studio:

How to add custom DB provider to this list?

UPD: If I use command string edmgen.exe I got error:

error 7001: Failed to find or load the registered .Net Framework Data Provider.

You need to declare the DbFactoryProvider in a config file (Web.config, Machine.config, etc). Here's a sample one I pulled from a project using MySQL:

<system.data>
  <DbProviderFactories>
    <remove invariant="MySql.Data.MySqlClient"/>
    <add name="MySQL Data Provider" invariant="MySql.Data.MySqlClient" description=".Net Framework Data Provider for MySQL" type="MySql.Data.MySqlClient.MySqlClientFactory, MySql.Data, Version=6.3.6.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d"/>
  </DbProviderFactories>
</system.data>

I also prefer declaring these in the application-level config files and have my apps use the local copy of the assembly. This helps with portability since we can't guarantee that the 3rd party provider is available in GAC.

Old(from 7 Fabruary 2013): It is impossible to add Npgsql provider to be accesible in Visual Studio, because NpgSql for now does not support DDEX.

Update on 29 of December 2013: It seems that DDEX support was added.

If you want to list up Npgsql in Datasource list in Visual Studio, this article may be a little helpful.

Anyway, since Visual Studio is delivered by Microsoft, obviously you need to work on the registry table.

From: http://fxjr.blogspot.com/2011/05/npgsql-design-time-support-preview.html

comes a very important step you have to make: Inside Npgsql.Designer2 folder, there is a file called NpgsqlProvider.gen.reg. You have to merge this file to your registry every time you start VS.Net to debug the project