两个DT比较

        /// <summary>
        /// 两个dt比较 B与A相同列相同值的重新更新到B
        /// </summary>
        /// <param name="dtA">总的dt(数据均为0)</param>
        /// <param name="dtB">当前dt(已经查询到的数据)</param>
        /// <returns>dtA</returns>
        private DataTable CompareDataTable(DataTable dtA, DataTable dtB)
        {
      

            for (int i = 0; i < dtB.Rows.Count; i++)
            {

                for (int j = 0; j < dtB.Columns.Count; j++)
                {

                    string categorynameB = Convert.ToString(dtB.Rows[i]["categoryname"]); //行业

                    for (int k = 0; k < dtA.Rows.Count; k++)
                    {

                        for (int m = 0; m < dtA.Columns.Count; m++)
                        {

                            string categorynameA = Convert.ToString(dtA.Rows[k]["categoryname"]); //行业

                            if (categorynameB == categorynameA)
                            {
                                string ColumnsB = dtB.Columns[j].ToString();

                                string ColumnsA = dtA.Columns[m].ToString();

                                if (ColumnsB == ColumnsA)
                                {

                                    dtA.Rows[k][m] = dtB.Rows[i][j];
                                }

                            }
                        }


                    }

                }

            }

            return dtA;
        }