The decimal problem in C is solved

Question:

startTime = DateTime.Now;                      
-----------
slExecutedTime.Text = (DateTime.Now - startTime).ToString();
Execution results:
Executed: 00:00:03.1234434 (lots of decimal places later)
Desired execution results:
Executed: 00:00:03

--------------------------------------------------------------------------------

Solution 1 (recommended) :

Related properties of TimeSpan:

 Related properties and functions 
Add : with the other 1 a TimeSpan Value added. 
Days: Returns the number of days TimeSpan Value. 
Duration: To obtain TimeSpan The absolute value of theta. 
Hours: Returns in hours TimeSpan value 
Milliseconds: Returns in milliseconds TimeSpan Value. 
Minutes: Returns in minutes TimeSpan Value. 
Negate: Returns the negative of the current instance. 
Seconds: Returns in seconds TimeSpan Value. 
Subtract: Subtract another from that 1 a TimeSpan Value. 
Ticks: return TimeSpan The value of the tick The number. 
TotalDays: return TimeSpan Value represents the number of days. 
TotalHours: return TimeSpan Value represents the number of hours. 
TotalMilliseconds: return TimeSpan Value represents the number of milliseconds. 
TotalMinutes: return TimeSpan The number of minutes represented by the value. 
TotalSeconds: return TimeSpan Value represents the number of seconds. 

/// <summary>
        ///  Program execution time test 
        /// </summary>
        /// <param name="dateBegin"> The start time </param>
        /// <param name="dateEnd"> The end of time </param>
        /// <returns> return ( seconds ) Units, such as : 0.00239 seconds </returns>
        public static string ExecDateDiff(DateTime dateBegin, DateTime dateEnd)
        {
            TimeSpan ts1 = new TimeSpan(dateBegin.Ticks);
            TimeSpan ts2 = new TimeSpan(dateEnd.Ticks);
            TimeSpan ts3 = ts1.Subtract(ts2).Duration();
            // You want to transfer the format 
            return ts3.TotalMilliseconds.ToString();
        }

That's the basic thing. You get milliseconds
If you just want the format that you want, you can just take the first 10 bits

ts3.ToString("g")     0:00:07.171
ts3.ToString("c")     00:00:07.1710000
ts3.ToString("G")     0:00:00:07.1710000
There are 3 formats to choose from, and I recommend that you use a truncated trial if you need one
Such as

ts3.ToString("g").Substring(0,8)   0:00:07.1
ts3.ToString("c").Substring(0,8)   00:00:07
ts3.ToString("G").Substring(0,8)   0:00:00

Option 2: more complicated

#region  Return time difference 
        public static string DateDiff(DateTime DateTime1, DateTime DateTime2)
        {
            string dateDiff = null;
            try
            {
                TimeSpan ts1 = new TimeSpan(DateTime1.Ticks);
                TimeSpan ts2 = new TimeSpan(DateTime2.Ticks);
                TimeSpan ts = ts1.Subtract(ts2).Duration();
                string hours = ts.Hours.ToString(), minutes = ts.Minutes.ToString(),seconds = ts.Seconds.ToString();
                if(ts.Hours<10)
                {
                    hours = "0" + ts.Hours.ToString();
                }
                if (ts.Minutes<10)
                {
                    minutes = "0" + ts.Minutes.ToString();
                }
                if(ts.Seconds<10)
                {
                    seconds = "0" + ts.Seconds.ToString();
                }
                dateDiff = hours + ":"+ minutes + ":"+ seconds;
            }
            catch
            {
            }
            return dateDiff;
        }
        #endregion

From: http: / / www. cnblogs. com hongfei/archive 2013/03/11/2953366. html