Excel 画像ファイル貼付

Excel.cs

namespace sample
{
    class Excel
    {
        dynamic excelApp = null;
        dynamic workBooks = null;
        dynamic workBook = null;
        dynamic workSheets = null;
        dynamic workSheet = null;
        dynamic range = null;
        dynamic shape = null;

        /// <summary>
        /// Excelファイルを新規作成
        /// </summary>
        /// <param name="excelfile">保存するExcelファイル名（フルパス）</param>
        /// <param name="imagefile">貼り付ける画像ファイル名（フルパス）</param>        
        public void MakeExcelFile(string excelfile, string imagefile)
        {
            try
            {
                Type excelApplication = Type.GetTypeFromProgID("Excel.Application");
                excelApp = Activator.CreateInstance(excelApplication);
                
                // 確認メッセージ非表示
                excelApp.DisplayAlerts = false;

                // ワークブック、シート定義
                workBooks = excelApp.WorkBooks;
                workBook = workBooks.Add();
                workSheets = workBook.Sheets;
                workSheet = workSheets["Sheet1"];

                // セルA2選択
                range = workSheet.Range["A2"];

                // 画像貼付
                double Left = range.Left;
                double Top = range.Top;
                double Width = 0;
                double Height = 0;

                shape = workSheet.Shapes.AddPicture(imagefile, true, true, Left, Top, Width, Height);
            	// 倍率を100%にする
                shape.ScaleHeight(1.0, true);
                shape.ScaleWidth(1.0, true);

                // Bookを別名で保存し、アプリ終了
                workBook.SaveAs(excelfile);
                workBook.Close();
                excelApp.Quit();
            }
            finally
            {
                releaseObject((object)shape);
                releaseObject((object)range);
                releaseObject((object)workSheet);
                releaseObject((object)workSheets);
                releaseObject((object)workBook);
                releaseObject((object)workBooks);
                releaseObject((object)excelApp);
            }
        }
        /// <summary>
        /// Excelオブジェクトリリース用
        /// </summary>
        /// <param name="obj">リリースするオブジェクト</param>
        private void releaseObject(object obj)
        {
            try
            {
                Marshal.FinalReleaseComObject(obj);
                obj = null;
            }
            catch (Exception e)
            {
                obj = null;
                MessageBox.Show("Can't Release Object " + e.ToString());
            }
            finally
            {
                GC.Collect();
            }
        }
    }
}