Thank you for the answer but that don't work.
If I put 10,25 and save it, the system return 10,25 (that's correct)
If I put 10.25 and save it, the system return 1025 (that's incorrect)
this is the code :
protected void Page_Load(object sender, EventArgs e)
{
Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;