'Exe-Datei
 
Class Main
Public SQLCon as new SQLClient.SQLConnection
Sub Connect
SQLCon = Login.SQLServer(Sender,DataSource,Catalog,Trusted,Database)
 
'Die Verbindung SQLCon steht ab hier nicht mehr zur Verfügung bzew. ist closed! 
' Warum?
'Ich finde den Fehler einfach nicht
 
End sub
End Class
 
 
'DLL
Class Login
Dim SQL as as new SQLClient.SQLConnection
Function SQL-Server(ByVal Sender as System.Windows.Forms.Form, ByVal DataSource _
  as String,byVal Catalog as String, ByVal Trusted as Boolean, DataBase as _
  String) as System.Data.SQLClient.SQLConnection
 
Dim UserName as String = "XYZ" 
Dim PWD as String = "ABC" 
 
SQL.ConnectionString = "Server=" & DataSource & ";DataBase=" & Catalog & ";User" & _
  "ID=" & Username & ";Trusted_Connection=" & Trusted & ""
 
Try
 SQL.open()
Catch ex as Exemption
 'MessageBox .....
End Try
 
Return SQL
 
End Function
End Class