先贴代码后简单解释：

        public static object[,] BuildTable(Stream inputStream)
        {
            object[,] table = null;
            using (var doc =
                SpreadsheetDocument.Open(
                    inputStream,false))
            {
                Sheet sheet = doc.WorkbookPart.Workbook.Descendants<Sheet>().FirstOrDefault();

                var worksheetPart = (WorksheetPart) doc.WorkbookPart.GetPartById(sheet.Id);

                var headers = worksheetPart.Worksheet.Descendants<Row>()
                                           .FirstOrDefault(x => x.RowIndex == 1);
                SheetData sheetData = worksheetPart.Worksheet.GetFirstChild<SheetData>();
                var allRows = sheetData.Elements<Row>()
                                       .Where(x => x.RowIndex > 1 && !string.IsNullOrEmpty(x.InnerText)).ToList();
                var headerCells = headers.Descendants<Cell>().ToList();
                var headerCellReferences =
                    headerCells.Select(c => Regex.Replace(c.CellReference,@"\d+",string.Empty)).ToArray();
                
                SharedStringTablePart sstPart = doc.WorkbookPart.GetPartsOfType<SharedStringTablePart>().First();
                SharedStringTable ssTable = sstPart.SharedStringTable;

                WorkbookStylesPart workbookStylesPart = doc.WorkbookPart.GetPartsOfType<WorkbookStylesPart>().First();

                CellFormats cellFormats = workbookStylesPart.Stylesheet.CellFormats;
                var headerStrings = headerCells.Select(c => ProcessCellValue(c,ssTable,cellFormats)).ToArray();
                table = new object[allRows.Count + 1,headerStrings.Length];
                //assign column title to the table
                for (int i = 0; i < headerStrings.Length; i++)
                {
                    table[0,i] = headerStrings[i];
                }

                //assign all cell values to the table
                for (int i = 0; i < allRows.Count; i++)
                {
                    var cells = allRows[i].Elements<Cell>().Select(c =>
                        {
                            c.CellReference = Regex.Replace(c.CellReference,string.Empty);
                            return c;
                        });
                    for (int j = 0; j < headerCells.Count; j++)
                    {
                        table[i + 1,j] =
                            ProcessCellValue(
                                cells.FirstOrDefault(
                                       c =>
                                       c.CellReference == headerCellReferences[j]),cellFormats);
                    }
                }
            }
            return table;
        }
        /// <summary>
        /// Process the valus of a cell and return a .NET value
        /// </summary>
        private static object ProcessCellValue(Cell c,SharedStringTable ssTable,CellFormats cellFormats)
        {
            if (c == null) return null;
            // If there is no data type,this must be a string that has been formatted as a number
            if (c.DataType == null)
            {
                if (c.CellValue == null) return string.Empty;
                if (c.StyleIndex == null) return c.CellValue.Text;
                CellFormat cf =
                    cellFormats.Descendants<CellFormat>()
                               .ElementAt<CellFormat>(Convert.ToInt32(c.StyleIndex.Value));
                if (cf.NumberFormatId >= 0 && cf.NumberFormatId <= 13) // This is a number
                {
                    return Convert.ToDecimal(c.CellValue.Text);
                }
                if (cf.NumberFormatId >= 14 && cf.NumberFormatId <= 22) // This is a date
                {
                    return DateTime.FromOADate(Convert.ToDouble(c.CellValue.Text));
                }
                return c.CellValue.Text;
            }

            switch (c.DataType.Value)
            {
                case CellValues.SharedString:
                    return ssTable.ChildElements[Convert.ToInt32(c.CellValue.Text)].InnerText;
                case CellValues.Boolean:
                    return c.CellValue.Text == "1";
                case CellValues.Date:
                    return DateTime.FromOADate(Convert.ToDouble(c.CellValue.Text));
                case CellValues.Number:
                    return Convert.ToDecimal(c.CellValue.Text);
                default:
                    return c.CellValue != null ? c.CellValue.Text : string.Empty;
            }
        }
        

主要值得提的是为什么要使用EXCEL的列头（如A,B,C,D）来取数据而不是用索引。如下面代码片断：

var headerCellReferences =
                    headerCells.Select(c => Regex.Replace(c.CellReference,string.Empty)).ToArray();

上面是把EXCEL中所有行的单元格的列头由A1,A2,B1,B2全部变成A,A,B，用于后期单元格定位。

如果当你某一列或多列EXCEL单元格是空值，那么取出来的单元格集合将不包含此列，因此集合的长度不确定， 我们不能用索引来取每一行特定单元格的值。

使用：

BuildTable(Request.Files["filename"].InputStream)

public static IEnumerable<T> BuildList<T>(object[,] table)
        {
            var list = new List<T>();
            Type t = typeof(T);
                PropertyInfo[] props = t.GetProperties();
            for (int i = 1; i < table.GetLength(0); i++)
            {
                var item = Activator.CreateInstance<T>();
                for (int j = 0; j < table.GetLength(1); j++)
                {
                    var title = Regex.Replace(table[0,j].ToString(),@"\s+",string.Empty);

                    var prop =
                        props.FirstOrDefault(p => p.Name.Equals(title,StringComparison.InvariantCultureIgnoreCase));
                    if (prop != null && table[i,j] != null && !string.IsNullOrEmpty(table[i,j].ToString().Trim()))
                    {
                        prop.SetValue(item,ConvertHelper.ChangeType(table[i,j],prop.PropertyType),null);
                    }
                }
                list.Add(item);
            }
            return list;
        } 

var table = ExcelHelper.BuildTable(file.InputStream);
            var students = ExcelHelper.BuildList<Student>(table);