title: Getting error: String reference not set to an instance of a String. Parameter name: s
body: <p>I am using this code to truncate datetime from my database into its year and time components. The variables YearOfRelease and Runtime contain datetime of the format       "dd/MM/yyyy hh:mm:ss" It was working fine previously but its now giving the error: </p>
  
  <p><strong>String reference not set to an instance of a String.
  Parameter name: s</strong></p>
  
  <p>It could only be something wrong in the DateTime.ParseExact function, could anyone please let me know why 'null' is suddenly causing this problem when previously it was working perfectly?</p>
  
  <pre><code>    DateTime dt2 = new DateTime();
  
  
      dt = DateTime.ParseExact(YearOfRelease, "dd/MM/yyyy hh:mm:ss", null);
  
      Year = dt.Year.ToString();
  
  
      dt2 = DateTime.ParseExact(RunTime, "dd/MM/yyyy hh:mm:ss", null);
      string hour = dt2.Hour.ToString();
      string min = dt2.Minute.ToString();
  
      Time = hour + ":" + min;
  </code></pre>