How to make friends Postgresql and EntityFramework?

Question

PostgreSQL

I will abstractly describe the situation: there is a project consisting of a class library in which data access is implemented and a web project on ASP.NET MVC. I want to make sure that in the web project there are no links to the Entity Framework, but only a link to a library with classes for data access. The reference library has Entity Framework, Npgsql and Npgsql.EntityFramework. The following is written in App.config of the library:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 --></configSections>
  <system.data>
    <DbProviderFactories>
      <remove invariant="Npgsql" />
      <add name="Npgsql Data Provider"
            invariant="Npgsql"
            description="Data Provider for PostgreSQL"
            type="Npgsql.NpgsqlFactory, Npgsql" />
    </DbProviderFactories>
  </system.data>
  <entityFramework>
    <defaultConnectionFactory type="Npgsql.NpgsqlFactory, Npgsql, Version=2.2.7.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />
    <providers>
      <provider invariantName="Npgsql" type="Npgsql.NpgsqlServices, Npgsql.EntityFramework, Version=2.2.7.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />
    </providers>
  </entityFramework>
</configuration>

In a web project, the web.config contains the following:

<configSections>
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <connectionStrings>
    <add name="Auth" connectionString="server=localhost;user id=username;password=password;database=Gullfoss.Auth" providerName="Npgsql" />
  </connectionStrings>
<system.data>
    <DbProviderFactories>
      <remove invariant="Npgsql" />
      <add name="Npgsql Data Provider"
            invariant="Npgsql"
            description="Data Provider for PostgreSQL"
            type="Npgsql.NpgsqlFactory, Npgsql, Version=2.2.7.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />
    </DbProviderFactories>
  </system.data>
  <entityFramework>
    <defaultConnectionFactory type="Npgsql.NpgsqlFactory, Npgsql, Version=2.2.7.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />
    <providers>
      <provider invariantName="Npgsql" type="Npgsql.NpgsqlServices, Npgsql.EntityFramework, Version=2.2.7.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />
    </providers>
  </entityFramework>

When starting the web application and trying to access the database, the following error occurs:

Failed to set Database.DefaultConnectionFactory to an instance of the 'Npgsql.NpgsqlFactory, Npgsql, Version=2.2.7.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7' type as specified in the application configuration. See inner exception for details.

The InnerException has the following:

Constructor on type 'Npgsql.NpgsqlFactory' not found.

Help me figure it out, I've been scratching my head over this problem all day and I can't solve it.

Answer 1

Problem solved. Updated npgsql to 3.0.7 ( https://www.nuget.org/packages/EntityFramework6.Np... and changed configs:

<entityFramework>
    <defaultConnectionFactory type="Npgsql.NpgsqlConnectionFactory, EntityFramework6.Npgsql" />
    <providers>
      <provider invariantName="Npgsql" type="Npgsql.NpgsqlServices, EntityFramework6.Npgsql" />
    </providers>
  </entityFramework>

  <system.data>
    <DbProviderFactories>
      <remove invariant="Npgsql" />
      <add name="Npgsql Data Provider" invariant="Npgsql" support="FF" description=".Net Framework Data Provider for Postgresql"
 type="Npgsql.NpgsqlFactory, Npgsql" />
    </DbProviderFactories>
  </system.data>

On the Internet I came across information, they say, it is correct to write like this:
I got this error because of this line.

Answer 2

no0ob and is connectionStrings also in .config? That link doesn't work either...

The format of the initialization string does not match the specification