How to customize cell value while exporting the Xamarin.Forms DataGrid into Excel and PDF?

private void ExportToPDF_Clicked(object sender, EventArgs e)
{
    isExporting = true;
    DataGridPdfExportingController pdfExport = new DataGridPdfExportingController();
    pdfExport.CellExporting += PdfExport_CellExporting;
    MemoryStream stream = new MemoryStream();
    var doc = pdfExport.ExportToPdf(this.dataGrid, new DataGridPdfExportOption()
    {
        FitAllColumnsInOnePage = true
    });
    doc.Save(stream);
    doc.Close(true);
    if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
        Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("DataGrid.pdf", "application/pdf", stream);
    else
        Xamarin.Forms.DependencyService.Get<ISave>().Save("DataGrid.pdf", "application/pdf", stream);
}
private void PdfExport_CellExporting(object sender, DataGridCellPdfExportingEventArgs e)
{
    if (e.CellValue is int && (int)e.CellValue == 10001)
    {
        e.CellValue = 99999;
    }
}

private void ExportToExcel_Clicked(object sender, EventArgs e)
{
    isExporting = true;
    DataGridExcelExportingController excelExport = new DataGridExcelExportingController();
    excelExport.CellExporting += ExcelExport_CellExporting;
    DataGridExcelExportingOption exportOption = new DataGridExcelExportingOption();
    if (Device.OS == TargetPlatform.iOS)
    {
        exportOption.ExportColumnWidth = false;
        exportOption.DefaultColumnWidth = 150;
    }
    var excelEngine = excelExport.ExportToExcel(this.dataGrid, exportOption);
    var workbook = excelEngine.Excel.Workbooks[0];
    MemoryStream stream = new MemoryStream();
    workbook.SaveAs(stream);
    workbook.Close();
    excelEngine.Dispose();
 
    if (Device.OS == TargetPlatform.WinPhone || Device.OS == TargetPlatform.Windows)
        Xamarin.Forms.DependencyService.Get<ISaveWindowsPhone>().Save("DataGrid.xlsx", "application/msexcel", stream);
    else
        Xamarin.Forms.DependencyService.Get<ISave>().Save("DataGrid.xlsx", "application/msexcel", stream);
}
private void ExcelExport_CellExporting(object sender, DataGridCellExcelExportingEventArgs e)
{
    if (e.CellValue is int && (int)e.CellValue == 10001)
    {
        e.CellValue = 99999;
    }
}

public interface ISave
{
    void Save(string filename, string contentType, MemoryStream stream);
}
public interface ISaveWindowsPhone
{
    Task Save(string filename, string contentType, MemoryStream stream);
}
public interface IAndroidVersionDependencyService
{
    int GetAndroidVersion();
}

public class SaveAndroid : ISave
{
    public void Save(string fileName, String contentType, MemoryStream stream)
    {
        string exception = string.Empty;
        string root = null;
        if (Android.OS.Environment.IsExternalStorageEmulated)
        {
            root = Android.OS.Environment.ExternalStorageDirectory.ToString();
        }
        else
            root = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
 
        Java.IO.File myDir = new Java.IO.File(root + "/Syncfusion");
        myDir.Mkdir();
 
        Java.IO.File file = new Java.IO.File(myDir, fileName);
 
        if (file.Exists()) file.Delete();
 
        try
        {
            FileOutputStream outs = new FileOutputStream(file);
            outs.Write(stream.ToArray());
 
            outs.Flush();
            outs.Close();
        }
        catch (Exception e)
        {
            exception = e.ToString();
        }
        if (file.Exists() && contentType != "application/html")
        {
            Android.Net.Uri path = Android.Net.Uri.FromFile(file);
            string extension = Android.Webkit.MimeTypeMap.GetFileExtensionFromUrl(Android.Net.Uri.FromFile(file).ToString());
            string mimeType = Android.Webkit.MimeTypeMap.Singleton.GetMimeTypeFromExtension(extension);
            Intent intent = new Intent(Intent.ActionView);
            intent.SetDataAndType(path, mimeType);
            Forms.Context.StartActivity(Intent.CreateChooser(intent, "Choose App"));
        }
    }
}

public class SaveIOS : ISave
{
    void ISave.Save(string filename, string contentType, MemoryStream stream)
    {
        string exception = string.Empty;
        string path = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
        string filePath = Path.Combine(path, filename);
        try
        {
            FileStream fileStream = File.Open(filePath, FileMode.Create);
            stream.Position = 0;
            stream.CopyTo(fileStream);
            fileStream.Flush();
            fileStream.Close();
        }
        catch (Exception e)
        {
            exception = e.ToString();
        }
        if (contentType == "application/html" || exception != string.Empty)
            return;
        UIViewController currentController = UIApplication.SharedApplication.KeyWindow.RootViewController;
        while (currentController.PresentedViewController != null)
            currentController = currentController.PresentedViewController;
        UIView currentView = currentController.View;
 
        QLPreviewController qlPreview = new QLPreviewController();
        QLPreviewItem item = new QLPreviewItemBundle(filename, filePath);
        qlPreview.DataSource = new PreviewControllerDS(item);
 
        //UIViewController uiView = currentView as UIViewController;
 
        currentController.PresentViewController((UIViewController)qlPreview, true, (Action)null);
    }
}

public class SaveWindows : ISaveWindowsPhone
{
    public async Task Save(string filename, string contentType, MemoryStream stream)
    {
        if (Device.Idiom != TargetIdiom.Desktop)
        {
            StorageFolder local = Windows.Storage.ApplicationData.Current.LocalFolder;
            StorageFile outFile = await local.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
            using (Stream outStream = await outFile.OpenStreamForWriteAsync())
            {
                outStream.Write(stream.ToArray(), 0, (int)stream.Length);
            }
            if (contentType != "application/html")
                await Windows.System.Launcher.LaunchFileAsync(outFile);
        }
        else
        {
            StorageFile storageFile = null;
            FileSavePicker savePicker = new FileSavePicker();
            savePicker.SuggestedStartLocation = PickerLocationId.Desktop;
            savePicker.SuggestedFileName = filename;
            switch (contentType)
            {
                case "application/vnd.openxmlformats-officedocument.presentationml.presentation":
                    savePicker.FileTypeChoices.Add("PowerPoint Presentation", new List<string>() { ".pptx", });
                    break;
 
                case "application/msexcel":
                    savePicker.FileTypeChoices.Add("Excel Files", new List<string>() { ".xlsx", });
                    break;
 
                case "application/msword":
                    savePicker.FileTypeChoices.Add("Word Document", new List<string>() { ".docx" });
                    break;
 
                case "application/pdf":
                    savePicker.FileTypeChoices.Add("Adobe PDF Document", new List<string>() { ".pdf" });
                    break;
                case "application/html":
                    savePicker.FileTypeChoices.Add("HTML Files", new List<string>() { ".html" });
                    break;
            }
            storageFile = await savePicker.PickSaveFileAsync();
 
            using (Stream outStream = await storageFile.OpenStreamForWriteAsync())
            {
                outStream.Write(stream.ToArray(), 0, (int)stream.Length);
                outStream.Flush();
                outStream.Dispose();
            }
            stream.Flush();
            stream.Dispose();
            await Windows.System.Launcher.LaunchFileAsync(storageFile);
        }
    }
}