Ge Total Free Space on a Drive (In KB - Tb)

private static long GetTotalFreeSpace(string sDriveName)
       {
           long nRet = -1;
           foreach (DriveInfo drive in DriveInfo.GetDrives())
           {
               if (drive.IsReady && drive.Name == sDriveName)
               {
                   nRet = drive.TotalFreeSpace;
               }
           }
           return nRet;
       }
 
       private static long GetTotalFreeSpace(string sDriveName, string sUnits)
       {
           long nDenominator = 1;
           switch (sUnits)
           {
               case "K":
                   nDenominator = 1024;
                   break;
               case "M":
                   nDenominator = 1048576;
                   break;
               case "G":
                   nDenominator = 1073741824;
                   break;
               case "T":
                   nDenominator = 1099511627776;
                   break;
               default:
                   break;
           }
 
 
           long nRet = -1;
           foreach (DriveInfo drive in DriveInfo.GetDrives())
           {
               if (drive.IsReady && drive.Name == sDriveName)
               {
                   nRet =(long) clsCommonStatics.ZeroDouble ((double) drive.TotalFreeSpace, (double)nDenominator) ;
               }
           }
           return nRet;
       }