title: ArgumentNullException: Argument cannot be null c#(Unity)
body: <p>Here is my code :</p>
  
  <pre><code>string playerwinnopairboth = "P  ";
  
  IEnumerator WinLog_big_road()
  {
      string[] historyvalue = { };
      historyvalue = tzPlayInfo.Instance.HistoryValue;
      /*-------------------------------*/
      NetworkManager.instance.WebSocketServer.OnCallBack_SC_WEBSOCKET_BcGametableHistory += CallBack_CS_WEBSOCKET_BcGametableHistory;
      /*-------------------------------*/
      DeleteChildrens(pos_big_road);
      yield return new WaitForEndOfFrame();
      for (int i = 0; i &lt; rh.Const._HISTORY_COUNT_CARD_ * rh.Const._HISTORY_DECK_; i++)
      {
          int x = i % rh.Const._HISTORY_COUNT_CARD_;
          int y = i / rh.Const._HISTORY_COUNT_CARD_;
  
          float xl = 2.0f;
          float yl = -5.0f;
  
          GameObject o = Instantiate(prefab_big_road) as GameObject;
          o.transform.SetParent(pos_big_road);
          o.transform.localScale = Vector3.one;
  
  
          o.transform.localPosition = new Vector3(x * xl, y * yl, 0f);
          if (historyvalue.Contains(playerwinnopairboth))
          {
              //o.GetComponent&lt;UISprite&gt;().spriteName = "layout_player_bigline-01";
              //NGUITools.SetActive(o, true);
              Debug.Log("PLAYER WIN, NO PAIR , NO PAIR");
          }
  }
  
  
  private void CallBack_CS_WEBSOCKET_BcGametableHistory(bool success, Int32 gametable_no, Int32 year, Int32 month, Int32 day, Int32 shoe_no, bc_gametable_history_list list)
  {
      string s1 = "";
      for (int i = 0; i &lt; tzPlayInfo.Instance.bc_gametable_history_list.Count; i++)
      {
          s1 += tzPlayInfo.Instance.bc_gametable_history_list[i].r;
          s1 += ",";
      }
      tzPlayInfo.Instance.HistoryValue = s1.ToString().Split(',');
  }
  </code></pre>
  
  <p>my <strong>tzPlayInfo</strong> values is like this:</p>
  
  <pre><code>private string[] historyvalue;
  public string[] HistoryValue
  {
      get { return historyvalue; }
      set { historyvalue = value; }
  
  }
  </code></pre>
  
  <p>The Error is pointing me out here</p>
  
  <pre><code> if (historyvalue.Contains(playerwinnopairboth))
          {
              //o.GetComponent&lt;UISprite&gt;().spriteName = "layout_player_bigline-01";
              //NGUITools.SetActive(o, true);
              Debug.Log("PLAYER WIN, NO PAIR , NO PAIR");
          }
  </code></pre>
  
  <p>I don't know why it's giving me a null value . Could someone point out what i am doing wrong here. Thank you in advance for those who will help me...</p>