PostgreSQL

GAC Installation

The generator is a T4 template that runs externally to your project and therefore cannot make use of any NuGet packages you have installed into your project. It can however use ones that are installed in the GAC. Therefore the PostgreSQL npgsql.dll file needs to be installed into the GAC to make it accessible to the generator.

Visit https://github.com/npgsql/npgsql/releases and download the latest MSI installer by looking into the assets of a release. The latest one with an MSI installer is currently v4.1.8

Tick the box on the installer to automatically install this into the GAC. If you missed it, you can manually install npgsql into the global assembly cache (GAC). Run the following command:

cd C:\Users\[user]\.nuget\packages\npgsql\4.1.3.0\lib\net461
gacutil.exe /i Npgsql.dll

Notice I am using the .NET 4.6.1 version because the generator runs as a T4 template using .NET, and not a .NET Core template. It does not matter if you are generating code for .NET or .NET Core, the generator is run outside of your project as a .NET program.

Looking at which version I have installed with gacutil /l npgsql shows the following:

Microsoft (R) .NET Global Assembly Cache Utility.  Version 4.0.30319.0
Copyright (c) Microsoft Corporation.  All rights reserved.

The Global Assembly Cache contains the following assemblies:
  npgsql, Version=4.1.3.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7, processorArchitecture=MSIL

Number of items = 1

Which means I have v4.1.3 installed.

machine.config

In both

• c:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config
• c:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config

at approximately line 168 I have the following <system.data> XML where you will see the Npgsql Data Provider has been added

<system.data>
    <DbProviderFactories>
      <add name="Microsoft SQL Server Compact Data Provider 4.0" invariant="System.Data.SqlServerCe.4.0" description=".NET Framework Data Provider for Microsoft SQL Server Compact" type="System.Data.SqlServerCe.SqlCeProviderFactory, System.Data.SqlServerCe, Version=4.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91"/>
      <add name="Npgsql Data Provider" invariant="Npgsql" description=".NET Data Provider for PostgreSQL" type="Npgsql.NpgsqlFactory, Npgsql, Version=4.1.8.0, Culture=neutral, PublicKeyToken=5D8B90D52F46FDA7"/>
      <add name="MySQL Data Provider" invariant="MySql.Data.MySqlClient" description=".Net Framework Data Provider for MySQL" type="MySql.Data.MySqlClient.MySqlClientFactory, MySql.Data, Version=9.0.0.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d"/>
      <add name="ODP.NET, Managed Driver" invariant="Oracle.ManagedDataAccess.Client" description="Oracle Data Provider for .NET, Managed Driver" type="Oracle.ManagedDataAccess.Client.OracleClientFactory, Oracle.ManagedDataAccess, Version=4.122.19.1, Culture=neutral, PublicKeyToken=89b483f429c47342"/>
      <add name="SQLite Data Provider" invariant="System.Data.SQLite" description=".Net Framework Data Provider for SQLite" type="System.Data.SQLite.SQLiteFactory, System.Data.SQLite" />
    </DbProviderFactories>
</system.data>

I modified both. However to find the exact one which is used by the generator, in your <database>.tt file very near the bottom, un-comment

fileManagement.WriteLine("// " + System.Runtime.InteropServices.RuntimeEnvironment.SystemConfigurationFile);

Save the <database>.tt and inspect the first line in the generated output. I have the following listed:

// C:\Windows\Microsoft.NET\Framework64\v4.0.30319\config\machine.config

So that is the exact file the generator will use, and is the one that is required to have the above npgsql XML added.

Further reading here.