How to Subtract the two date in C#- C-Sharp

here we subtract the two date start date and end date and store in a variavle in Number of Days Format

//First we extract the ate from data table and store in a variable

  string endt=dt.Rows[(dt.Rows.Count - 1)]["DATE_FIELD"].ToString() ;  //It gives the END Date in '14-May-2012' Format
  
  string stdt =dt.Rows[0]["DATE_FIELD"].ToString();   // //It gives the Start Date in '14-May-2012' Format 
                    
  int daydiff = 0;   // Initialize the variable

  // In the below case we subtract the date and store in a variavle in day format, like how many number of days
  daydiff = Convert.ToInt32( Convert.ToDateTime(endt).ToString("yyyyMMdd")) -Convert.ToInt32( Convert.ToDateTime(stdt).ToString("yyyyMMdd"));