How to calculate difference between two date in ASP.NET with C#

         TimeSpan tspan;
         DateTime date1 = Convert.ToDateTime(txtDateFrom.Text);
         DateTime date2 = Convert.ToDateTime(txtDateTo.Text);
         if (date1 > date2)
             tspan = date1.Subtract(date2);
         else
             tspan = date2.Subtract(date1);
         int days = Convert.ToInt32(tspan.TotalDays);

How to get first day of month in ASP.NET

DateTime date = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1);