c# - Add a value to dictionary within a dictionary error -

I am using the following code:

  private dictionary & lt; String, user & gt; Total Users = New Dictionary & lt; String, user & gt; ();   
 Part of the "user" category  
  personal dictionary & lt; DateTime, String & gt; KillerField; Public dictionary & lt; Date time, string & gt; The killed players (get {this.killerField;} set {this.killerField = value;}}   
 How am I trying to do this action  
  Total users [playerName] .killedPlayers.Add (DateTime.Now, die);   
 But I'm getting an error:  
  " Object reference is not set to an object instance "  
 Why is not it working?  
 Thanks in advance.   
 
 
 get you a  killerfield  Defeat Before You Can Add  Addition  Anything at the point of adding a player, it is still using the  new dictionary & lt; date time, string & gt; ()   
 You can do this as part of the announcement or alternatively in the class creator.