i m making a project in which i have to calculate total number of days from starting date to ending date which are inserted in text box by user at run time in asp.net c#.i have to do this on button_click event.how to do this? i tried this-

protected void TextBox14_TextChanged(object sender, EventArgs e)
{
    // get date from first text box

    DateTime dold = Convert.ToDateTime(TextBox1.Text);
    DateTime dnew = Convert.ToDateTime(TextBox14.Text);
    TimeSpan daydif = (dnew - dold);
    double dayd = daydif.TotalDays;
    Label27.Text = dayd.ToString();
}