C#、VSTO讀取Excel類

之前寫的類存在Excel進程不能結束的Bug，重寫ExcelReader類，類實例清理時Excel進程自動結束。

    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[1];

            // 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 = 1; 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 = 0; i < arr.GetLength(0); i++)
            {
                DataRow dr = dataTable.NewRow();
                for (int j = 0; j < arr.GetLength(1); j++)
                {
                    if (arr[i + 1, j + 1] != null)
                        dr[j] = arr[i + 1, j + 1];
                    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 > 0)
            {
                var modulo = (dividend - 1) % 26;
                columnName = Convert.ToChar(65 + modulo) + columnName;
                dividend = (dividend - modulo) / 26;
            }

            return columnName;
        }
        #endregion
    }