class ExcelReader

     {

         // Excel Object

         public Application app;

         public Workbooks wbs;

         public Workbook wb;

         public Worksheet ws;

         public Range rng;

         private bool disposed = false;

         public ExcelReader()

         {

             // New Excel Application

             app = new Application

             {

                 Visible = false,

                 DisplayAlerts = false

             };

         }

         /// <summary>

         /// 關閉對象

         /// </summary>

         public void Close()

         {

             Dispose();

         }

         /// <summary>

         /// 清理對象

         /// </summary>

         public void Dispose()

         {

             Dispose(true);

             GC.SuppressFinalize(this);

         }

         /// <summary>

         /// 清理所有正在使用的资源。

         /// </summary>

         /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param>

         protected virtual void Dispose(bool disposing)

         {

             if (disposed)

             {

                 return;

             }

             if (disposing)

             {

                 // Excel Application Quit

                 app.Quit();

                 // Finally, Release app.

                 System.Runtime.InteropServices.Marshal.FinalReleaseComObject(app);

                 app = null;

                 disposed = true;

             }

         }

         #region Worksheet Operation

         /// <summary>

         /// 從工作表讀取數據到 DataTable

         /// </summary>

         /// <param name="fileName">文件</param>

         /// <param name="sheet">工作表名</param>

         /// <returns>DataTable</returns>

         public DataTable GetDataTableFromSheet(string fileName, string sheet, int rows, int cols)

         {

             // Create Table

             DataTable dt = new DataTable();

             // Get Excel's WorkBooks. Attention: Don't use .Net cascade, ex.: app.Workbooks.Add()

             // Every variable Must set to reference, then Release it one by one.

             // If not, Can't quit Excel Process.

             wbs = app.Workbooks;

             // Get WorkBook

             wb = wbs.Open(fileName);

             // Get WorkSheet

             ws = wb.Sheets[sheet];

             // Columns & Rows Count

             //int colCount = ws.UsedRange.CurrentRegion.Columns.Count;

             //int rowCount = ws.UsedRange.CurrentRegion.Rows.Count;

             // Get worksheet's used range

             //rng = ws.UsedRange;

             rng = ws.Range[ws.Range["A1"], ws.Range[GetColumnName(cols)+rows]];

             dt = GetDataTableFromRange(rng, rows, cols);

             // Relase Range, Set to null. (variable reference that COM Object's Count is 0)

             System.Runtime.InteropServices.Marshal.FinalReleaseComObject(rng);

             rng = null;

             // Release WorkSheet

             System.Runtime.InteropServices.Marshal.FinalReleaseComObject(ws);

             ws = null;

             // Release WorkBook

             System.Runtime.InteropServices.Marshal.FinalReleaseComObject(wb);

             wb = null;

             // Release WorkBooks

             System.Runtime.InteropServices.Marshal.FinalReleaseComObject(wbs);

             wbs = null;

             return dt;

         }

         #endregion

         #region Range Operation

         /// <summary>

         /// 從單元格範圍讀取數據到 DataTable

         /// </summary>

         /// <param name="range">單元格範圍</param>

         /// <returns>DataTable</returns>

         private DataTable GetDataTableFromRange(Range range, int rows, int cols)

         {

             DataTable dataTable = new DataTable();

             // First Row Range

             Range titleRange = range.Rows[];

             // Columns Count

             //int colCount = titleRange.CurrentRegion.Columns.Count;

             // Title Row has Empty Cell Or Replication, Use Excel Column Header.

             if (titleRange.Cells.Cast<Range>().Any(s => s.Value2 == null)

                 || titleRange.Cells.Cast<Range>().GroupBy(s => s.Value2).Count() != titleRange.Cells.Count

                 || titleRange.CurrentRegion.Columns.Count != cols)

             {

                 for (int i = ; i <= cols; i++)

                 {

                     dataTable.Columns.Add(GetColumnName(i), typeof(string));

                 }

             }

             else

                 dataTable = GetTableStructureFromTitleRange(range);

             // Release Range Object

             System.Runtime.InteropServices.Marshal.FinalReleaseComObject(titleRange);

             titleRange = null;

             // Insert Data To DataTable Wtih Range Value

             object[,] arr = range.Value;

             for (int i = ; i < arr.GetLength(); i++)

             {

                 DataRow dr = dataTable.NewRow();

                 for (int j = ; j < arr.GetLength(); j++)

                 {

                     if (arr[i + , j + ] != null)

                         dr[j] = arr[i + , j + ];

                     else

                         dr[j] = "";

                 }

                 dataTable.Rows.Add(dr);

             }

             return dataTable;

         }

         /// <summary>

         /// 生成表頭。如果首行表頭規範，則採用首行表頭，否則用Excel表頭代替

         /// </summary>

         /// <param name="titleRow">首行範圍</param>

         /// <param name="isAllString">全部採用字符串格式</param>

         /// <returns>DataTable</returns>

         private DataTable GetTableStructureFromTitleRange(Range titleRow, bool isAllString = true)

         {

             DataTable dataTable = new System.Data.DataTable();

             foreach (Range cell in titleRow.Cells)

             {

                 if (isAllString)

                     dataTable.Columns.Add(cell.Value2, typeof(string));

                 else

                     dataTable.Columns.Add(cell.Value2, typeof(object));

             }

             return dataTable;

         }

         #endregion

         #region Column Operation

         /// <summary>

         /// 使用 Excel 標頭的方式生成字母列頭

         /// </summary>

         /// <param name="index">索引號</param>

         /// <returns>字母列頭</returns>

         public string GetColumnName(int index)

         {

             var dividend = index;

             var columnName = string.Empty;

             while (dividend > )

             {

                 var modulo = (dividend - ) % ;

                 columnName = Convert.ToChar( + modulo) + columnName;

                 dividend = (dividend - modulo) / ;

             }

             return columnName;

         }

         #endregion

     }