I need to connect to a PostgreSQL database from within PowerShell scripts. But how to install npgsql WITHOUT VisualStudio? There is no nuget!

So I tried to install the driver in the GAC using the newest MSI file (Npgsql-3.0.5.msi).

Using gacutil.exe shows, that it is installed:

Npgsql, Version=3.0.5.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7, processorArchitecture=MSIL

But PowerShell does not know anything about it! Get-Module -ListAvailable should show it but:

PS C:\WINDOWS\system32> (gmo -l n*).Name

NetAdapter  
NetConnection  
NetEventPacketCapture  
NetLbfo  
NetNat  
NetQos  
NetSecurity  
NetSwitchTeam  
NetTCPIP  
NetWNV  
NetworkConnectivityStatus  
NetworkLoadBalancingClusters  
NetworkTransition  
NFS  
PS C:\WINDOWS\system32> _

There is no module Npgsql!

I was searching for Npgsql.dll and it is there:

PS  C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Npgsql\v4.0_3.0.5.0__5d8b90d52f46fda7> dir

Verzeichnis: C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Npgsql\v4.0_3.0.5.0__5d8b90d52f46fda7


Mode                LastWriteTime     Length Name
----                -------------     ------ ----
-a---        08.01.2016     08:10     446464 Npgsql.dll


PS C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Npgsql\v4.0_3.0.5.0__5d8b90d52f46fda7> _

Because of the not recognised module npgsql my PowerShell code does not work:

function getDBConnection ($MyDBServer, $MyDBPort, $MyDatabase, $MyUid, $MyPwd) {
  $DBConnectionString = "Provider=PostgreSQL OLE DB Provider;Data Source=$MyDBServer;location=$MyDatabase;User ID=$MyUid;password=$MyPwd;timeout=1000;"
  $DBConn = New-Object System.Data.OleDb.OleDbConnection;
  $DBConn.ConnectionString = $DBConnectionString
  try {
    $DBConn.Open
  } catch {
    "Failed to connect! Error: "+ $_.Exception.Message
  }

  return $DBConn
}

function closeDBConnection ($DBConn) {
  $DBConn.Close
}

$query = "select * from test_table1"
$MyDBConnection = getDBConnection "dbserver" 5432 "databasename" "user" "pass"

try {
  $cmd = New-Object System.Data.OleDb.OleDbCommand($query, $MyDBConnection)
} catch {
  "Failed to create command object! Error: " + $_.Exception.Message
}
...

The $DBConn.Open doesn't fail, but the property ConnectionState remains Closed after the Open call.

The creation of an instance of OleDbCommand crashes with a german error message:

Failed to create command object! Error: Für "OleDbCommand" und die folgende Argumenteanzahl kann keine Überladung gefunden werden: "2".

It means that there are no overloaded methods with two parameters.

QUESTIONS:

• What do I need to install/configure so that Npgsql is visible in PowerShell?
• How do I load/import the Npgsql module in a PowerShell script or module?