解析Excel----ExcelHelper

public static class ExcelHelper
    {
        /// <summary>
        /// 获取单元格的值
        /// </summary>
        /// <param name="sheet">Excel sheet表名称</param>
        /// <param name="rowIndex">行索引</param>
        /// <param name="cellIndex">列索引</param>
        /// <returns>行索引和列索引从0开始</returns>
        ///这个方法是用来检查如果你不知道你的单元格里的值是什么类型的就可以用这个方法检查
        ///返回的字符串代表了单元格内容的值类型
        public static string GetCellValue(this ISheet sheet, int rowIndex, int cellIndex)
        {
            string returnValue = string.Empty;
            //拼接的条件
            if (sheet != null)
            {
                //如果当前的sheet不等于空  则获取索引行的值
                var row = sheet.GetRow(rowIndex);
                if (row != null)
                {
                    //如果行内容不为空 则获取列
                    var cell = row.GetCell(cellIndex);
                    if (cell != null)
                    {
                        //列也不为空则判断列中的值的类型
                        switch (cell.CellType)
                        {
                            //如果为string类型，则返回String类型
                            case CellType.String:
                                returnValue = cell.StringCellValue;
                                break;
                            //如果是数字类类型
                            case CellType.Numeric:
                                //判断是否为日期类型
                                if (DateUtil.IsCellDateFormatted(cell))
                                {
                                    //是日期类型则转化成日期输出
                                    returnValue = DateTime.FromOADate(cell.NumericCellValue).ToString();
                                }
                                else
                                {
                                    //输出数字类型
                                    returnValue = Convert.ToDouble(cell.NumericCellValue).ToString();
                                }
                                break;
                            //是否是bool类型
                            case CellType.Boolean:
                                returnValue = Convert.ToString(cell.BooleanCellValue);
                                break;
                            //错误函数类型
                            case CellType.Error:
                                returnValue = ErrorEval.GetText(cell.ErrorCellValue);
                                break;
                            case CellType.Formula:
                                switch (cell.CachedFormulaResultType)
                                {
                                    case CellType.String:
                                        string strFORMULA = cell.StringCellValue;
                                        if (strFORMULA != null && strFORMULA.Length > 0)
                                        {
                                            returnValue = strFORMULA.ToString();
                                        }
                                        break;
                                    case CellType.Numeric:
                                        returnValue = Convert.ToString(cell.NumericCellValue);
                                        break;
                                    case CellType.Boolean:
                                        returnValue = Convert.ToString(cell.BooleanCellValue);
                                        break;
                                    case CellType.Error:
                                        returnValue = ErrorEval.GetText(cell.ErrorCellValue);
                                        break;
                                    default:
                                        break;
                                }
                                break;
                            default:

                                break;
                        }
                    }
                }
            }
            return returnValue.Trim();
        }
        /// <summary>
        /// Excel导入
        /// </summary>
        /// <typeparam name="T">这个方法是将Excle转化成泛型导入</typeparam>
        /// <param name="columns">数组形式 列头</param>
        /// <param name="excelStream">文件流</param>
        /// <param name="excelType">文件类型</param>
        /// <returns>这是Excel导入List泛型导入</returns>
        public static List<T> ReadExcel<T>(string[] columns, Stream excelStream, string excelType = ".xlsx")
        {
            //先建立一个泛型
            var result = new List<T>();
            int j=0, k=0;
            try
            {
                //创建一个空的文件薄
                IWorkbook workbook = null;
                //如果文件类型为xlsx
                //做这个判断使检测Excel的版本的
                if (excelType == ".xlsx")
                {
                    //空的文件博等于XSSFWorkbook读取文件流
                    workbook = new XSSFWorkbook(excelStream);
                }
                else
                {
                    //如果是.xls就是HSSFWorkbook读取文件流  
                    workbook = new HSSFWorkbook(excelStream);
                }
                //工作簿是否大于零？如果大于零获取第一个工作薄的内容，否则空值
                ISheet sheet = workbook.NumberOfSheets > 0 ? workbook.GetSheetAt(0) : null;
                if (sheet == null)
                {
                    //工作薄如果为空值  转化失败
                    return result;
                }
                //这里定义的是反射类型
                var type = typeof(T);
                //遍历工作薄的内容
                
                for (j = 1; j <= sheet.LastRowNum-1; j++)//第一行默认是表头再去掉后面的说明的1行
                {

                    //动态创建动态类
                    var model = Activator.CreateInstance(type);
                    //行的值来自于sheet获取坐标为j的内容 因为第一行默认为表头，所以j从1开始
                    IRow row = sheet.GetRow(j);
                    if (row != null)
                    {
                        //columns导入的Excel标题头  
                        for ( k = 0; k < columns.Length; k++)
                        {
                            //pro得到的列头的类型
                            var pro = type.GetProperty(columns[k]);
                            if (pro != null)
                            {
                                //声明一个弱类型
                                Object value;
                                //列值获取
                                ICell cell = row.GetCell(k);
                                //处理获取到的列值类型
                                switch (cell.CellType)
                                {
                                    case CellType.Blank: //空数据类型处理
                                        value = null;
                                        break;
                                    case CellType.String: //字符串类型
                                        value = cell.StringCellValue;
                                        break;
                                    case CellType.Numeric: //数字类型                                   
                                        if (DateUtil.IsCellDateFormatted(cell))//日期类型
                                        {
                                            value = cell.DateCellValue;
                                        }
                                        else//其他数字类型
                                        {
                                            value = cell.NumericCellValue;
                                        }
                                        break;
                                    case CellType.Formula:
                                        HSSFFormulaEvaluator e = new HSSFFormulaEvaluator(workbook);
                                        value = e.Evaluate(cell).StringValue;
                                        break;
                                    default:
                                        value = null;
                                        break;
                                }
                                if (value != null)
                                {

                                    if (pro.GetType().Name == typeof(string).Name)
                                    {
                                        //插入值
                                        pro.SetValue(model, Convert.ChangeType(value.ToString(), pro.PropertyType), null);
                                    }
                                    else
                                        pro.SetValue(model, Convert.ChangeType(value, pro.PropertyType), null);
                                }
                            }
                        }
                        //将得到的值插入到T中（将T强制转化为Model类）
                        result.Add((T)model);
                    }
                }
            }
            catch (Exception ex)
            {
                throw new Exception("excel读取失败:第"+j+"行第"+k+"列数据错误：", ex);
            }
            return result;
        }

        /// <summary>
        /// 将sheet中的数据导出到datatable中
        /// </summary>
        /// <param name="sheet">需要导出的sheet</param>
        /// <param name="HeaderRowIndex">表头所在行号，-1表示没有表头</param>
        /// <returns>将Excel导出成Datatable</returns>
        private static DataTable ImportDt(ISheet sheet, int HeaderRowIndex, bool needHeader)
        {
            //新创建一个datatable
            DataTable table = new DataTable();
            IRow headerRow;
            int cellCount;
            try
            {
                //表头索引小于零时  输出表头
                if (HeaderRowIndex < 0 || !needHeader)
                {
                    //获取行索引为sheet表第一行
                    headerRow = sheet.GetRow(0);
                    //获取不为空的列个数
                    cellCount = headerRow.LastCellNum;
                    //获取第一列的值
                    for (int i = headerRow.FirstCellNum; i <= cellCount; i++)
                    {
                        DataColumn column = new DataColumn(Convert.ToString(i));
                        table.Columns.Add(column);
                    }
                }
                else
                {
                    //获取行内容
                    headerRow = sheet.GetRow(HeaderRowIndex);
                    cellCount = headerRow.LastCellNum;
                    //获取第一行第一个单元格内容
                    for (int i = headerRow.FirstCellNum; i <= cellCount; i++)
                    {
                        if (headerRow.GetCell(i) == null)
                        {
                            if (table.Columns.IndexOf(Convert.ToString(i)) > 0)
                            {
                                DataColumn column = new DataColumn(Convert.ToString("重复列名" + i));
                                table.Columns.Add(column);
                            }
                            else
                            {
                                DataColumn column = new DataColumn(Convert.ToString(i));
                                table.Columns.Add(column);
                            }

                        }
                        else if (table.Columns.IndexOf(headerRow.GetCell(i).ToString()) > 0)
                        {
                            DataColumn column = new DataColumn(Convert.ToString("重复列名" + i));
                            table.Columns.Add(column);
                        }
                        else
                        {
                            DataColumn column = new DataColumn(headerRow.GetCell(i).ToString());
                            table.Columns.Add(column);
                        }
                    }
                }
                int rowCount = sheet.LastRowNum;
                for (int i = (HeaderRowIndex + 1); i <= sheet.LastRowNum; i++)
                {
                    try
                    {
                        IRow row;
                        if (sheet.GetRow(i) == null)
                        {
                            row = sheet.CreateRow(i);
                        }
                        else
                        {
                            row = sheet.GetRow(i);
                        }

                        DataRow dataRow = table.NewRow();

                        for (int j = row.FirstCellNum; j <= cellCount; j++)
                        {
                            try
                            {
                                if (row.GetCell(j) != null)
                                {
                                    switch (row.GetCell(j).CellType)
                                    {
                                        case CellType.String:
                                            string str = row.GetCell(j).StringCellValue;
                                            if (str != null && str.Length > 0)
                                            {
                                                dataRow[j] = str.ToString();
                                            }
                                            else
                                            {
                                                dataRow[j] = null;
                                            }
                                            break;
                                        case CellType.Numeric:
                                            if (DateUtil.IsCellDateFormatted(row.GetCell(j)))
                                            {
                                                dataRow[j] = DateTime.FromOADate(row.GetCell(j).NumericCellValue);
                                            }
                                            else
                                            {
                                                dataRow[j] = Convert.ToDouble(row.GetCell(j).NumericCellValue);
                                            }
                                            break;
                                        case CellType.Boolean:
                                            dataRow[j] = Convert.ToString(row.GetCell(j).BooleanCellValue);
                                            break;
                                        case CellType.Error:
                                            dataRow[j] = ErrorEval.GetText(row.GetCell(j).ErrorCellValue);
                                            break;
                                        case CellType.Formula:
                                            switch (row.GetCell(j).CachedFormulaResultType)
                                            {
                                                case CellType.String:
                                                    string strFORMULA = row.GetCell(j).StringCellValue;
                                                    if (strFORMULA != null && strFORMULA.Length > 0)
                                                    {
                                                        dataRow[j] = strFORMULA.ToString();
                                                    }
                                                    else
                                                    {
                                                        dataRow[j] = null;
                                                    }
                                                    break;
                                                case CellType.Numeric:
                                                    dataRow[j] = Convert.ToString(row.GetCell(j).NumericCellValue);
                                                    break;
                                                case CellType.Boolean:
                                                    dataRow[j] = Convert.ToString(row.GetCell(j).BooleanCellValue);
                                                    break;
                                                case CellType.Error:
                                                    dataRow[j] = ErrorEval.GetText(row.GetCell(j).ErrorCellValue);
                                                    break;
                                                default:
                                                    dataRow[j] = "";
                                                    break;
                                            }
                                            break;
                                        default:
                                            dataRow[j] = "";
                                            break;
                                    }
                                }
                            }
                            catch (Exception exception)
                            {
                                throw new Exception(exception.Message);
                            }
                        }
                        table.Rows.Add(dataRow);
                    }
                    catch (Exception exception)
                    {
                        throw new Exception(exception.Message);
                    }
                }
            }
            catch (Exception exception)
            {
                throw new Exception(exception.Message);
            }
            return table;
        }
    }