利用NPOI读取Excel

     本文主要提供了一个利用NPOI读取一个Excel的实际值的类。本文使用的NPOI版本为1.2.5，NPOI.dll可以到NPOI的官网http://npoi.codeplex.com/下载。如果有写得不当的地方，希望能得到大家的斧正。

using System;
using System.Collections.Generic;
using System.Text;

using System.Data;
using System.IO;
using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;

namespace Common.Excel
{
    public static class NPOIHandler
    {
        public static DataSet ExcelToDataSet(string excelPath)
        {
            return ExcelToDataSet(excelPath, true);
        }

        public static DataSet ExcelToDataSet(string excelPath, bool firstRowAsHeader)
        {
            int sheetCount;
            return ExcelToDataSet(excelPath, firstRowAsHeader, out sheetCount);
        }

        public static DataSet ExcelToDataSet(string excelPath, bool firstRowAsHeader, out int sheetCount)
        {
            using (DataSet ds = new DataSet())
            {
                using (FileStream fileStream = new FileStream(excelPath, FileMode.Open, FileAccess.Read))
                {
                    HSSFWorkbook workbook = new HSSFWorkbook(fileStream);

                    HSSFFormulaEvaluator evaluator = new HSSFFormulaEvaluator(workbook);

                    sheetCount = workbook.NumberOfSheets;

                    for (int i = 0; i < sheetCount; ++i)
                    {
                        HSSFSheet sheet = workbook.GetSheetAt(i) as HSSFSheet;
                        DataTable dt = ExcelToDataTable(sheet, evaluator, firstRowAsHeader);
                        ds.Tables.Add(dt);
                    }

                    return ds;
                }
            }
        }

        public static DataTable ExcelToDataTable(string excelPath, string sheetName)
        {
            return ExcelToDataTable(excelPath, sheetName, true);
        }

        public static DataTable ExcelToDataTable(string excelPath, string sheetName, bool firstRowAsHeader)
        {
            using (FileStream fileStream = new FileStream(excelPath, FileMode.Open, FileAccess.Read))
            {
                HSSFWorkbook workbook = new HSSFWorkbook(fileStream);

                HSSFFormulaEvaluator evaluator = new HSSFFormulaEvaluator(workbook);

                HSSFSheet sheet = workbook.GetSheet(sheetName) as HSSFSheet;

                return ExcelToDataTable(sheet, evaluator, firstRowAsHeader);
            }
        }

        private static DataTable ExcelToDataTable(HSSFSheet sheet, HSSFFormulaEvaluator evaluator, bool firstRowAsHeader)
        {
            if (firstRowAsHeader)
            {
                return ExcelToDataTableFirstRowAsHeader(sheet, evaluator);
            }
            else
            {
                return ExcelToDataTable(sheet, evaluator);
            }
        }

        private static DataTable ExcelToDataTableFirstRowAsHeader(HSSFSheet sheet, HSSFFormulaEvaluator evaluator)
        {
            using (DataTable dt = new DataTable())
            {
                HSSFRow firstRow = sheet.GetRow(0) as HSSFRow;
                int cellCount = GetCellCount(sheet);

                for (int i = 0; i < cellCount; i++)
                {
                    if (firstRow.GetCell(i) != null)
                    {
                        dt.Columns.Add(firstRow.GetCell(i).StringCellValue ?? string.Format("F{0}", i + 1), typeof(string));
                    }
                    else
                    {
                        dt.Columns.Add(string.Format("F{0}", i + 1), typeof(string));
                    }
                }

                for (int i = 1; i <= sheet.LastRowNum; i++)
                {
                    HSSFRow row = sheet.GetRow(i) as HSSFRow;
                    DataRow dr = dt.NewRow();
                    FillDataRowByHSSFRow(row, evaluator, ref dr);
                    dt.Rows.Add(dr);
                }

                dt.TableName = sheet.SheetName;
                return dt;
            }
        }

        private static DataTable ExcelToDataTable(HSSFSheet sheet, HSSFFormulaEvaluator evaluator)
        {
            using (DataTable dt = new DataTable())
            {
                if (sheet.LastRowNum != 0)
                {
                    int cellCount = GetCellCount(sheet);

                    for (int i = 0; i < cellCount; i++)
                    {
                        dt.Columns.Add(string.Format("F{0}", i), typeof(string));
                    }

                    for (int i = 0; i < sheet.FirstRowNum; ++i)
                    {
                        DataRow dr = dt.NewRow();
                        dt.Rows.Add(dr);
                    }

                    for (int i = sheet.FirstRowNum; i <= sheet.LastRowNum; i++)
                    {
                        HSSFRow row = sheet.GetRow(i) as HSSFRow;
                        DataRow dr = dt.NewRow();
                        FillDataRowByHSSFRow(row, evaluator, ref dr);
                        dt.Rows.Add(dr);
                    }
                }

                dt.TableName = sheet.SheetName;
                return dt;
            }
        }

        private static void FillDataRowByHSSFRow(HSSFRow row, HSSFFormulaEvaluator evaluator, ref DataRow dr)
        {
            if (row != null)
            {
                for (int j = 0; j < dr.Table.Columns.Count; j++)
                {
                    HSSFCell cell = row.GetCell(j) as HSSFCell;

                    if (cell != null)
                    {
                        switch (cell.CellType)
                        {
                            case CellType.BLANK:
                                dr[j] = DBNull.Value;
                                break;
                            case CellType.BOOLEAN:
                                dr[j] = cell.BooleanCellValue;
                                break;
                            case CellType.NUMERIC:
                                if (DateUtil.IsCellDateFormatted(cell))
                                {
                                    dr[j] = cell.DateCellValue;
                                }
                                else
                                {
                                    dr[j] = cell.NumericCellValue;
                                }
                                break;
                            case CellType.STRING:
                                dr[j] = cell.StringCellValue;
                                break;
                            case CellType.ERROR:
                                dr[j] = cell.ErrorCellValue;
                                break;
                            case CellType.FORMULA:
                                cell = evaluator.EvaluateInCell(cell) as HSSFCell;
                                dr[j] = cell.ToString();
                                break;
                            default:
                                throw new NotSupportedException(string.Format("Catched unhandle CellType[{0}]", cell.CellType));
                        }
                    }
                }
            }
        }

        private static int GetCellCount(HSSFSheet sheet)
        {
            int firstRowNum = sheet.FirstRowNum;

            int cellCount = 0;

            for (int i = sheet.FirstRowNum; i <= sheet.LastRowNum; ++i)
            {
                HSSFRow row = sheet.GetRow(i) as HSSFRow;

                if (row != null && row.LastCellNum > cellCount)
                {
                        cellCount = row.LastCellNum;
                }
            }

            return cellCount;
        }
    }
}