Convert yyyymmdd (int ) to Datetime and Datetime to yyyymmdd in C#

string _StartDate = "20120707";
 if (!String.IsNullOrEmpty(StartDate))
      {
            DateTime _ExpiryDate = DateTime.ParseExact(_StartDate, "yyyyMMdd", DateTimeFormatInfo.InvariantInfo);
         }


This will convert 20120707 to 7/7/2012 12:00:00 AM


Now given _ExpiryDate as 7/7/2012 12:00:00 AM, The following will convert from Date to yyyymmdd format


 _ExpiryDate.ToString("yyyyMMdd", System.Globalization.CultureInfo.GetCultureInfo("en-US"));