.Net Core NPOI 导出多级表头的实现代码

using npoi.hssf.usermodel;
using npoi.ss.usermodel;
using npoi.ss.util;
using system.data;
using system.text.regularexpressions;
namespace testconsoleapp
{
    /// <summary>
    /// 导出excel
    /// </summary>
    public static class exporthelper
    {
        public static void export()
        {
            var dt = cretetable();
            var titles = getexceltitles(dt.columns, out int maxtitlelevel);
            hssfworkbook workbook = new hssfworkbook();
            isheet sheet = workbook.createsheet("sheet1");
            var allrowcount = dt.rows.count + maxtitlelevel;
            //创建所有单元格
            for (int i = 0; i < allrowcount; i++)
            {
                var row = sheet.createrow(i);
                for (int j = 0; j < dt.columns.count; j++)
                {
                    row.createcell(j);
                }
            }
            //合并创建表头
            foreach (var tit in titles)
            {
                sheet.getrow(tit.startrow).getcell(tit.startcolumn).setcellvalue(tit.title);
                if (tit.mergecolumncount + tit.mergerowcount > 0)
                {
                    sheet.addmergedregion(new cellrangeaddress(tit.startrow, tit.startrow + tit.mergerowcount, tit.startcolumn, tit.startcolumn + tit.mergecolumncount));
                }
            }
            //生成数据行
            for (int i = 0; i < dt.rows.count; i++)
            {
                for (int j = 0; j < dt.columns.count; j++)
                {
                    string cellvalue = dt.rows[i][j].tostring();
                   sheet.getrow(maxtitlelevel + i).cells[j].setcellvalue(cellvalue);
                }
            }
            using filestream stm = file.openwrite(@"d:\drivers\merge.xls");
            workbook.write(stm);
        }
        private static datatable cretetable()
        {
            datatable dt = new datatable();
            dt.columns.add("编号");
            dt.columns.add("收入-线上采购-数量");
            dt.columns.add("收入-线上采购-金额");
            dt.columns.add("收入-线下采购-数量");
            dt.columns.add("收入-线下采购-金额");
            dt.columns.add("回收-数量");
            dt.columns.add("回收-金额");
            dt.columns.add("支出-测试01-数量");
            dt.columns.add("支出-测试01-金额");
            dt.columns.add("支出-测试02-数量");
            dt.columns.add("支出-测试02-金额");
            dt.columns.add("其它-数量");
            dt.columns.add("其它-金额");
            dt.columns.add("备注");
            for (int i = 1; i <= 100; i++)
            {
                var row = dt.newrow();
                row["编号"] = "编号" + i;
                row["收入-线上采购-数量"] = i;
                row["收入-线上采购-金额"] = i;
                row["收入-线下采购-数量"] = i;
                row["收入-线下采购-金额"] = i;
                row["回收-数量"] = i;
                row["回收-金额"] = i;
                row["支出-测试01-数量"] = i;
                row["支出-测试01-金额"] = i;
                row["支出-测试02-数量"] = i;
                row["支出-测试02-金额"] = i;
                row["其它-数量"] = i;
                row["其它-金额"] = i;
                row["备注"] = i;
                dt.rows.add(row);
            }
            return dt;
        }
        private static list<exceltitle> getexceltitles(datacolumncollection columns, out int maxtitlelevel)
        {
            maxtitlelevel = 0;
            list<levelexceltitle> levelexceltitles = new list<levelexceltitle>();
            for (var index = 0; index < columns.count; index++)
            {
                var column = columns[index].tostring();
                var arr = column.split("-");
                if (maxtitlelevel < arr.length)
                {
                    maxtitlelevel = arr.length;
                }
                for (int i = 0; i < arr.length; i++)
                {
                    levelexceltitles.add(new levelexceltitle()
                    {
                        title = arr[i],
                        levelcode = string.join("-", arr[..(i + 1)]),
                        rowindex = i,
                        columnindex = index,
                        totallevel = arr.length
                    });
                }
            }
            var titlelevel = maxtitlelevel;
            var exceltitles = levelexceltitles
                .groupby(b => new
                {
                    b.levelcode,
                    b.title
                })
               .select(b => new exceltitle()
               {
                   title = b.key.title,
                   startrow = b.min(c => c.rowindex),
                   mergerowcount = b.min(c => c.rowindex) + 1 == b.max(c => c.totallevel) ? titlelevel - b.max(c => c.totallevel) : 0,
                   startcolumn = b.min(c => c.columnindex),
                   mergecolumncount = b.count() - 1,//排除自身
               }).tolist();
            return exceltitles;
        }
    }
    public class exceltitle
    {
        /// <summary>
        /// 标题
        /// </summary>
        public string title { get; set; }
        /// <summary>
        /// 开始行
        /// </summary>
        public int startrow { get; set; }
        /// <summary>
        /// 合并行
        /// </summary>
        public int mergerowcount { get; set; }
        /// <summary>
        /// 开始列
        /// </summary>
        public int startcolumn { get; set; }
        /// <summary>
        /// 合并列
        /// </summary>
        public int mergecolumncount { get; set; }
    }
    public class levelexceltitle
    {
        /// <summary>
        /// 标题
        /// </summary>
        public string title { get; set; }
        public string levelcode { get; set; }
        /// <summary>
        /// 第几行
        /// </summary>
        public int rowindex { get; set; }
        /// <summary>
        /// 第几列
        /// </summary>
        public int columnindex { get; set; }
        /// <summary>
        /// 总层
        /// </summary>
        public int totallevel { get; set; }
    }
}