地圖輸出柵格圖片的簡單方法，返回輸出的檔案名稱

/// <summary>
        /// 地圖輸出柵格圖片的簡單方法，返回輸出的檔案名稱
        /// </summary>
        /// <param name="pActiveView"></param>
        /// <returns></returns>
        public  static string  ExportImage(IActiveView pActiveView)
        {

            if (pActiveView == null)
            {
                return "";
            }
 
            SaveFileDialog pSaveFileDialog = new SaveFileDialog();
            pSaveFileDialog.Filter = "JPEG(*.jpeg)|*.jpeg|AI(*.ai)|*.ai|BMP(*.BMP)|*.bmp|EMF(*.emf)|*.emf|GIF(*.gif)          |*.gif|PDF(*.pdf)|*.pdf|PNG(*.png)|*.png|EPS(*.eps)|*.eps|SVG(*.svg)|*.svg|TIFF(*.tif)|*.tif";
            pSaveFileDialog.Title = "輸出地圖";
            pSaveFileDialog.RestoreDirectory = true;
            pSaveFileDialog.FilterIndex = 1;
 
            if (pSaveFileDialog.ShowDialog() != System.Windows.Forms.DialogResult.OK)
            {
                return "";
            }
            string FileName = pSaveFileDialog.FileName;
           
            IExport pExporter = null;
            switch (pSaveFileDialog.FilterIndex)
            {
                case 1:
                    pExporter = new ExportJPEGClass();
                    break;
                case 2:
                    pExporter = new ExportBMPClass();
                    break;
                case 3:
                    pExporter = new ExportEMFClass();
                    break;
                case 4:
                    pExporter = new ExportGIFClass();
                    break;
 
                case 5:
                    pExporter = new ExportAIClass();
                    break;
 
                case 6:
                    pExporter = new ExportPDFClass();
                    break;
                case 7:
                    pExporter = new ExportPNGClass();
                    break;
                case 8:
                    pExporter = new ExportPSClass();
                    break;
                case 9:
                    pExporter = new ExportSVGClass();
                    break;
                case 10:
                    pExporter = new ExportTIFFClass();
                    break;
                default:
                    MessageBox.Show("輸出格式錯誤");
                    return null;
 
            }
 
            int pResolution = (int)(pActiveView.ScreenDisplay.DisplayTransformation.Resolution);

            tagRECT ptagRECT = pActiveView.ExportFrame;//注意該處的代碼，改為其他會出錯

            IEnvelope pEnvelope = new EnvelopeClass();
            pEnvelope.PutCoords(ptagRECT.left, ptagRECT.bottom, ptagRECT.right, ptagRECT.top);

            ITrackCancel pTrackCancel = new CancelTrackerClass();

            pExporter.Resolution = pResolution;
            pExporter.ExportFileName = FileName;
            pExporter.PixelBounds = pEnvelope;

            pActiveView.Output(pExporter.StartExporting(), pResolution, ref ptagRECT, pActiveView.Extent, pTrackCancel);
            pExporter.FinishExporting();
            pExporter.Cleanup();
          
            //釋放資源
            pSaveFileDialog.Dispose();
 
            System.Runtime.InteropServices.Marshal.ReleaseComObject(pExporter);
 
            return FileName;

}