dataviewrow的问题

 foreach (DataRowView drv in dv)

            {

                if (tn == null)

                {

                    //提示我没有将对象引用实例化

                    tn.Text =  drv["c_Name"].ToString();

                    tn.Value = drv["fatherCol"].ToString();

                    this.tvList.Nodes.Add(tn);

                    BindTreeNode(Int32.Parse(drv["fatherCol"].ToString()), tn1);

                }

                else

                {

                    tn1 = new TreeNode();

                    tn1.Text = drv["c_Name"].ToString();

                    tn1.Value = drv["fatherCol"].ToString();

                    tn.ChildNodes.Add(tn1);

                    BindTreeNode(Int32.Parse(drv["fatherCol"].ToString()),tn);

                }

            }

可是我的 dataviewrow 里面明明只有数据的。
drv.Row.ItemArray[0] 数组长度明明是2  可是 就是娶不到值
------最佳解决方案--------------------
 if (tn == null)
                {
                  tn.xxxx = //这样不出错才怪

------其他解决方案--------------------
 if (tn != null)