Private Sub cbo_SelectUser_SelectedValueChanged(sender As Object, e As _
  EventArgs) Handles cbo_SelectUser.SelectedValueChanged
        cbo_SelectUser.Text.ToString() ' Gefüllte Combobox mit übergabe
        DB_SQL = "SELECT UserName(" & _
          "cbo_SelectUser.Text.ToString),Kuerzel,Pass,SysRoll FROM user" 'SQL 
        ' Abfrage nach user Auswahl
        DB_Command.CommandText = DB_SQL
        DB_Conn_Open()
        DB_Command.ExecuteReader()
        While (DB_Reader.Read())
            txb_Username.Text = (DB_Reader("UserName")) 'Benutzername
            txb_Kuerzel.Text = (DB_Reader("Kuerzel")) 'Benutzerkürzel
            txb_Password.Text = (DB_Reader("Pass")) 'Passwort
            cbo_Sysroll.Text = (DB_Reader("SysRoll"))'Systemrolle
        End While
        DB_Conn_Close()
    End Sub

EALA FREYA FRESENA

SELECT UserName,Kuerzel,Pass,SysRoll FROM user 
WHERE UserName = " & cbo_SelectUser.Text & "

DB_Command.ExecuteReader()

Private Sub cbo_SelectUser_SelectedValueChanged(sender As Object, e As _
  EventArgs) Handles cbo_SelectUser.SelectedValueChanged
    Dim objDR As SqlClient.SqlDataReader
    Dim ConnectionString As String = "DEIN CONNECTION STRING"
    Dim objConnection As SqlClient.SqlConnection
 
    objConnection = New SqlClient.SqlConnection(ConnectionString)
    Dim objCmd As New SqlClient.SqlCommand("SELECT" & _
      "UserName,Kuerzel,Pass,SysRoll FROM user 
WHERE UserName = @User", objConnection)
    objcmd.Parameters.AddWithValue("@User", cbo_SelectUser.Text)
 
    If objConnection.State <> ConnectionState.Open Then
    objConnection.Open()
    End If
    objDR = objCommand.ExecuteReader(CommandBehavior.CloseConnection)
    objCommand = Nothing
 
    If objDR.HasRows Then
    While objDR.Read()
            txb_Username.Text = (objDR("UserName")) 'Benutzername
            txb_Kuerzel.Text = (objDR("Kuerzel")) 'Benutzerkürzel
            txb_Password.Text = (objDR("Pass")) 'Passwort
            cbo_Sysroll.Text = (objDR("SysRoll"))'Systemrolle
    End While
    End If
    objDR.Close()
    objDR = Nothing
end sub

Dim DB_Reader As MySqlDataReader
        DB_SQL = String.Format("SELECT UserName,Kuerzel,Pass,SysRoll FROM user" & _
          "WHERE UserName = @User")
        DB_Command.Parameters.AddWithValue("@User", cbo_SelectUser.Text)
        DB_Command.CommandText = DB_SQL
 
        If DB_Connection.State <> ConnectionState.Open Then
        DB_Conn_Open() 'Ist im Modul -> database schon fertig.
        End If
        DB_Reader = DB_Command.ExecuteReader(CommandBehavior.CloseConnection)
        If DB_Reader.HasRows = True Then
            While DB_Reader.Read()
                txb_Username.Text = (DB_Reader("UserName"))
                txb_Kuerzel.Text = (DB_Reader("Kuerzel"))
                txb_Password.Text = (DB_Reader("Pass"))
                cbo_Sysroll.Text = (DB_Reader("SysRoll"))
            End While
        End If
        DB_Conn_Close()'Ist im Modul -> database schon fertig.

DB_Command.Parameters.AddWithValue("@User", cbo_SelectUser.Text)

 DB_Reader = DB_Command.ExecuteReader(CommandBehavior.CloseConnection)
        If DB_Reader.HasRows = True Then
            While DB_Reader.Read()
                txb_Username.Text = (DB_Reader("UserName"))
                txb_Kuerzel.Text = (DB_Reader("Kuerzel"))
                txb_Password.Text = (DB_Reader("Pass"))
                cbo_Sysroll.Text = (DB_Reader("SysRoll"))
            End While
        End If

Dim mSQL As String = "SELECT DISTINCT (Auftragsnummer), (Kunde) FROM" & _
  "[Auftraege];"
Dim oDS_AftrNr As DataSet = New DataSet()
Dim TempAdapter = New MySqlDataAdapter(mSQL, ConnString)
TempAdapter.Fill(oDS_AftrNr)
 
DeinDGV.DataSource = oDS_AftrNr.Tables(0)

Zitat:

Ich hoffe du willst kein DGV mittels DataReader befüllen?