System.ArgumentNullException: Value cannot be null. Parameter name: String at System.Number.ParseDouble(String s, NumberStyles style, NumberFormatInfo info) at System.Double.Parse(String s, NumberStyles style, IFormatProvider provider) at System.Double.Parse(String s) at hastravel_new.booking.Page_Load(Object sender, EventArgs e) in E:\www.hastravel.com\booking.aspx.cs:line 1601