datatable 设置数据时发生错误

错误描述是这样 
object reference not set to an instance ofan object代码//创建表
        public static void Initialization()
        {
            _TimeDataCollection = new DataTable();
        
            _TimeDataCollection.Columns.Add(new DataColumn("Code"));
            _TimeDataCollection.Columns.Add(new DataColumn("Time"));
            _TimeDataCollection.Columns.Add(new DataColumn("Index"));
        }        private static void SaveToDataTable(object obj)
        {
            TimeDataStuctue TDS = (TimeDataStuctue)obj;//TimeDataStuctue 是自己定义的类型            DataRow DR;            string expression = string.Format("Code = '{0}' and Index ='{1}'", TDS.Code, TDS.Index.ToString());
            DataRow[] foundRows = new DataRow[0];
            lock (_TimeDataCollection)
            {
                try
                {
                    // Use the Select method to find all rows matching the filter.
                    foundRows = _TimeDataCollection.Select(expression);                    if (foundRows.Length > 0)
                    {
                        DR = foundRows[0];
                    }
                    else
                    {
                        DR = _TimeDataCollection.NewRow();
                        _TimeDataCollection.Rows.Add(DR);
                    }
                }
                catch (Exception e)
                {
                    OnExceptionHappend(e, "SaveToDataTable.FoundRows." + TDS.Code);//传出错误报告
                    return;
                }
            }
            try
            {
                DR["Code"] = TDS.Code;//string 类型
                DR["Time"] = TDS.Time.ToString("HH:mm:ss");//DateTime 类型
                DR["Index"] = TDS.Index.ToString();//int 类型
            }
            catch (Exception e)
            {
                OnExceptionHappend(e, "SaveToDataTable.SetRow" + TDS.Code);//传出错误报告，也是发生错误的地方
                return;
            }
        }