Private Sub login()
 
        If string.IsNullOrEmpty(txbUserName.Text) Then
            MessageBox.Show("Fehler","Sie müssen einen Benutzernamen" & _
              "eingeben.", MessageBoxButtons.OK, MessageBoxIcon.Information)
            Exit Sub
        ElseIf txbUserPassword.TextLength <= 0 Then
            MessageBox.Show("Fehler","Sie müssen ein Passwort eingeben.", _
              MessageBoxButtons.OK, MessageBoxIcon.Information)
            Exit Sub
        End If
 
        Dim con As New MySqlClient.MySqlConnection( _
          "server=xxxx;user=xxxx;password=xxxx;database=xxxx;")
        Dim query As New MySqlClient.MySqlCommand("SELECT uid FROM user WHERE" & _
        "username =?username AND password = md5(?password) LIMIT 1", con )
 
        Try
          con.Open()
          query.Parameters.AddWithValue("?username", txbUserName.Text)
          query.Parameters.AddWithValue("?password", txbUserPassword.Text)
 
          DIM result as Object = query.ExecuteScalar()
 
            'Prüfroutine
            If result IsNot Nothing Then
            ' erfolgreich eingeloggt
                MessageBox.Show("....")
                Me.Close()
            Else
                MessageBox.Show("....")
                Exit Sub
            End If
            '----------------------------
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        Finally
            con.Close()
        End Try
    End Sub