DataTable extended column conversion method (2*2 matrix conversion)

 

Source data is shown in the figure

// <summary>
        /// DataTable扩展 列转行方法（2*2矩阵转换）
        /// </summary>
        /// <param name="dtSource">数据源</param>
        /// <param name="columnFilter">逗号分隔 如SDateTime,PM25,PM10,O3,NO2,SO2,CO 第一个参数为行，其余为要转换的列</param>
        /// <returns></returns>
        public static DataTable PivotDatatableColToRow(this DataTable dtSource, string columnFilter)
        {
            var columns = columnFilter.Split(',');
            DataTable dtFilter = dtSource.DefaultView.ToTable(false, columns);
            DataTable dtResult = new DataTable();

            var rowCount = dtFilter.Rows.Count;
            var columnCount = columns.Length;

            // 源数组的行数比DataTable的行数+1,, 加一行表头
            object[,] arrSource = new object[rowCount + 1, columnCount];

            // 目标数组的行数等于选择的列数,列数等于 源数据的行数+1, 加一列 属性名
            object[,] arrResult = new object[columnCount, rowCount + 1];

            // 原数组第一行写表头
            for (int i = 0; i < columnCount; i++)
            {
                arrSource[0, i] = dtFilter.Columns[i].ColumnName;
            }

            // 源数据 每一行写 数据
            for (int i = 0; i < rowCount; i++)
            {
                for (int j = 0; j < columnCount; j++)
                {
                    arrSource[i + 1, j] = dtFilter.Rows[i][j];
                }
            }

            // 原数 转置到 目标数组
            for (int i = 0; i < rowCount + 1; i++)
            {
                for (int j = 0; j < columnCount; j++)
                {
                    arrResult[j, i] = arrSource[i, j];
                }
            }

            // 创建 Datatable 的结构
            for (int i = 0; i < rowCount + 1; i++)
            {
                if (!dtResult.Columns.Contains(arrResult[0, i].ToString())) {
                    dtResult.Columns.Add(arrResult[0, i].ToString());
                }
            }

            List<string> valueList = new List<string>();
            for (int i = 1; i < columnCount; i++)
            {
                for (int j = 0; j < rowCount + 1; j++)
                {
                    valueList.Add(arrResult[i, j].ToString());
                }

                dtResult.Rows.Add(valueList.ToArray());
                valueList.Clear();
            }
            return dtResult;
        }

 converted data

DataTable newdt = dt.AsEnumerable().Where(p => p.Field<string>("City") == "武汉").CopyToDataTable().PivotDatatableColToRow("SDateTime,PM25,PM10,O3,NO2,SO2,CO");