NPOI读取Excel

namespace NQJExcelHelper
{

    public class SDExcelHelper
    {
        public static DataTable GetDataTable(string filepath)
        {
            DataTable dt = new DataTable();
            if (filepath.Last() == 's')
            {
                dt = ExcelHelper.ExcelToTableForXLS(filepath);
            }
            else
            {
                dt = ExcelHelper.ExcelToTableForXLSX(filepath);
            }
            return dt;
        }
        public class ExcelHelper
        {
            #region Excel2007
            /// <summary>
            /// 将Excel文件中的数据读出到DataTable中(xlsx)
            /// </summary>
            /// <param name="file"></param>
            /// <returns></returns>
            public static DataTable ExcelToTableForXLSX(string file)
            {
                DataTable dt = new DataTable();
                using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
                {
                    XSSFWorkbook xssfworkbook = new XSSFWorkbook(fs);
                    ISheet sheet = xssfworkbook.GetSheetAt(0);

                    //表头
                    IRow header = sheet.GetRow(sheet.FirstRowNum);
                    List<int> columns = new List<int>();
                    for (int i = 0; i < header.LastCellNum; i++)
                    {
                        object obj = GetValueTypeForXLSX(header.GetCell(i) as XSSFCell);
                        if (obj == null || obj.ToString() == string.Empty)
                        {
                            dt.Columns.Add(new DataColumn("Columns" + i.ToString()));

                        }
                        else
                            dt.Columns.Add(new DataColumn(obj.ToString()));
                        columns.Add(i);
                    }
                    //数据
                    for (int i = sheet.FirstRowNum + 1; i <= sheet.LastRowNum; i++)
                    {
                        DataRow dr = dt.NewRow();
                        bool hasValue = false;
                        foreach (int j in columns)
                        {
                            if (sheet.GetRow(i) != null)
                            {
                                dr[j] = GetValueTypeForXLSX(sheet.GetRow(i).GetCell(j) as XSSFCell);
                                if (dr[j] != null && dr[j].ToString() != string.Empty)
                                {
                                    hasValue = true;
                                }
                            }
                        }
                        if (hasValue)
                        {
                            dt.Rows.Add(dr);
                        }
                    }
                }
                return dt;
            }

            /// <summary>
            /// 将DataTable数据导出到Excel文件中(xlsx)
            /// </summary>
            /// <param name="dt"></param>
            /// <param name="file"></param>
            public static void TableToExcelForXLSX(DataTable dt, string file)
            {
                XSSFWorkbook xssfworkbook = new XSSFWorkbook();
                ISheet sheet = xssfworkbook.CreateSheet("Test");

                //表头
                IRow row = sheet.CreateRow(0);
                for (int i = 0; i < dt.Columns.Count; i++)
                {
                    ICell cell = row.CreateCell(i);
                    cell.SetCellValue(dt.Columns[i].ColumnName);
                }

                //数据
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    IRow row1 = sheet.CreateRow(i + 1);
                    for (int j = 0; j < dt.Columns.Count; j++)
                    {
                        ICell cell = row1.CreateCell(j);
                        cell.SetCellValue(dt.Rows[i][j].ToString());
                    }
                }

                //转为字节数组
                MemoryStream stream = new MemoryStream();
                xssfworkbook.Write(stream);
                var buf = stream.ToArray();

                //保存为Excel文件
                using (FileStream fs = new FileStream(file, FileMode.Create, FileAccess.Write))
                {
                    fs.Write(buf, 0, buf.Length);
                    fs.Flush();
                }
            }

            /// <summary>
            /// 获取单元格类型(xlsx)
            /// </summary>
            /// <param name="cell"></param>
            /// <returns></returns>
            private static object GetValueTypeForXLSX(XSSFCell cell)
            {
                if (cell == null)
                    return null;
                switch (cell.CellType)
                {
                    case CellType.Blank: //BLANK:
                        return null;
                    case CellType.Boolean: //BOOLEAN:
                        return cell.BooleanCellValue;
                    case CellType.Numeric: //NUMERIC:
                        return cell.NumericCellValue;
                    case CellType.String: //STRING:
                        return cell.StringCellValue;
                    case CellType.Error: //ERROR:
                        return cell.ErrorCellValue;
                    case CellType.Formula: //FORMULA:
                        if (cell.CachedFormulaResultType == CellType.Numeric)
                        {
                            return cell.NumericCellValue;
                        }
                        else
                        {
                            return cell.StringCellValue;
                        }
                    default:
                        return "=" + cell.CellFormula;
                }
            }

            #endregion

            #region Excel2003
            public static DataTable ExcelToTableForXLS(string file)
            {
                DataTable dt = new DataTable();
                using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
                {
                    HSSFWorkbook hssfworkbook = new HSSFWorkbook(fs);
                    ISheet sheet = hssfworkbook.GetSheetAt(0);

                    //表头
                    IRow header = sheet.GetRow(sheet.FirstRowNum);
                    List<int> columns = new List<int>();
                    for (int i = 0; i < header.LastCellNum; i++)
                    {
                        object obj = GetValueTypeForXLS(header.GetCell(i) as HSSFCell);
                        if (obj == null || obj.ToString() == string.Empty)
                        {
                            dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
                        }
                        else
                            dt.Columns.Add(new DataColumn(obj.ToString()));
                        columns.Add(i);
                    }
                    //数据
                    for (int i = sheet.FirstRowNum + 1; i <= sheet.LastRowNum; i++)
                    {
                        DataRow dr = dt.NewRow();
                        bool hasValue = false;
                        foreach (int j in columns)
                        {
                            if (sheet.GetRow(i) != null)
                            {
                                dr[j] = GetValueTypeForXLS(sheet.GetRow(i).GetCell(j) as HSSFCell);
                                if (dr[j] != null && dr[j].ToString() != string.Empty)
                                {
                                    hasValue = true;
                                }
                            }
                        }
                        if (hasValue)
                        {
                            dt.Rows.Add(dr);
                        }
                    }
                }
                return dt;

            }
            private static object GetValueTypeForXLS(HSSFCell cell)
            {
                if (cell == null)
                    return null;
                switch (cell.CellType)
                {
                    case CellType.Blank: //BLANK:
                        return null;
                    case CellType.Boolean: //BOOLEAN:
                        return cell.BooleanCellValue;
                    case CellType.Numeric: //NUMERIC:
                        return cell.NumericCellValue;
                    case CellType.String: //STRING:
                        return cell.StringCellValue;
                    case CellType.Error: //ERROR:
                        return cell.ErrorCellValue;
                    case CellType.Formula: //FORMULA:
                        if (cell.CachedFormulaResultType == CellType.Numeric)
                        {
                            return cell.NumericCellValue;
                        }
                        else
                        {
                            return cell.StringCellValue;
                        }
                    default:
                        return "=" + cell.CellFormula;
                }
            }

            #endregion
        }
    }
}