How to export a SfDataGrid to excel or PDF using ToolBarItems of a Page?

<ContentPage.ToolbarItems WidthRequest="100"
                           HeightRequest="50">
    <ToolbarItem Text="DOWNLOADASEXCEL" 
                 Order="Primary" 
                 Priority="0" 
                 Activated="ExcelExport_Activated"/>
    <ToolbarItem Text="DOWNLOADASPDF" 
                 Order="Primary" 
                 Priority="0" 
                 Activated="PDFExport_Activated"/>
</ContentPage.ToolbarItems>
 

private void ExcelExport_Activated(object sender, EventArgs e)
{
     isExporting = true;
     DataGridExcelExportingController excelExport = new DataGridExcelExportingController();
     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();
     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 PDFExport_Activated(object sender, EventArgs e)
{
     isExporting = true;
     DataGridPdfExportingController pdfExport = new DataGridPdfExportingController();
     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);
        }

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

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 = System.Environment.GetFolderPath(System.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);
        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);
       }
   }
}