// partType : 
//    0 - Hours, 
//    1 - Minutes, 
//    2 - Seconds, 
//    3 - Hours.Minutes (HH.MM)
//    4 - All (HH:MM:SS)
private string GetTimeBetweenDates(DateTime firstDate, 
           DateTime secondDate, int partType)
{
    string returnDate = null;
    if ( firstDate < secondDate )
    {
        TimeSpan spanDiff = secondDate.Subtract(firstDate);   
        int Hours   = spanDiff.Hours;
        int Minutes = spanDiff.Minutes;
        string strMinutes = string.Empty;
        int Seconds = spanDiff.Seconds;
 
        // Fix minutes
        switch (Minutes)
        {
          case 1: case 2: case 3: case 4: case 5: case 6:
                strMinutes = "0" + Minutes;
                break;
          default:
                strMinutes = Minutes.ToString();
                break;
        }
                                    
        //return value
        switch (partType)
        {
           case 0:
                 returnDate = Hours.ToString();
                 break;
           case 1:
                 returnDate = strMinutes;
                 break;
           case 2:
                 returnDate = Seconds.ToString();
                 break;
           case 3:
                 returnDate = Hours + "." + strMinutes;
                 break;
           case 4:
                 returnDate = Hours + ":" + strMinutes + ":" + Seconds;
                 break;
         }
    }
    // return date                
    return (returnDate);
 }
 
 private void AddTimeToDate(double dbTime, ref DateTime OriginalDate)
 {
   string[] SplitTimeToAdd = dbTime.ToString().Split('.');
   double Hours = Convert.ToDouble(SplitTimeToAdd[0].ToString());
               
   // Add the hours
   OriginalDate = OriginalDate.AddHours(Hours);
                 
   // Do some conversion on minutes
   // .0x -> Reads 5 minutes,
   // .x0  -> Reads 50 minutes
   // .xx -> Reads 33 minutes
   // .00 -> Reads 0 minutes
   double Minutes = 0.0;
                  
   // Convert the minutes section to an array of chars
   if ( SplitTimeToAdd.Length > 1 )
   {
     if ( SplitTimeToAdd[1].Length >= 1 )
     {           
       // .x case
       if ( (SplitTimeToAdd[1].Length == 1) )
          Minutes = (Convert.ToDouble(SplitTimeToAdd[1].ToString()) * 10 );
       else
          Minutes = Convert.ToDouble(SplitTimeToAdd[1].ToString());
                              
       // Add the calculated minutes
       OriginalDate = OriginalDate.AddMinutes(Minutes);
     }
   }
   else
     // Add the calculated minutes
     OriginalDate = OriginalDate.AddMinutes(Minutes);
}