private async void BtnuploadFile_ClickAsync(object sender, RoutedEventArgs e)
    {
       FileOpenPicker openPicker = new FileOpenPicker();
       openPicker.ViewMode = PickerViewMode.Thumbnail;
       openPicker.SuggestedStartLocation = PickerLocationId.Desktop;
       openPicker.FileTypeFilter.Add(".jpg");
       openPicker.FileTypeFilter.Add(".mp4");

        file = await openPicker.PickSingleFileAsync();
        if (file != null)
        {
            try {

            StorageFolder localFolder =     Windows.Storage.ApplicationData.Current.LocalFolder;

                StorageFolder appFolder = await Windows.Storage.ApplicationData.Current.LocalFolder.CreateFolderAsync("SubFolder", Windows.Storage.CreationCollisionOption.OpenIfExists);
                string folderName = System.IO.Path.GetFileNameWithoutExtension(file.Name);  //folder name with filename
                string desiredFolderNm = string.Empty;
                try
                {
                    desiredFolderNm = folderName;
                    //show here messagebox that is exists
                    Windows.UI.Xaml.Controls.ContentDialog replacePromptDialog = new Windows.UI.Xaml.Controls.ContentDialog()
                    {
                        Title = "Upload Video",
                        Content = "Do you want to upload file?",
                        CloseButtonText = "No",
                        PrimaryButtonText = "Yes"
                    };
                    Windows.UI.Xaml.Controls.ContentDialogResult result = await replacePromptDialog.ShowAsync();
                    if (result == Windows.UI.Xaml.Controls.ContentDialogResult.Primary)
                    {

                      StorageFolder newFolder = await appFolder.CreateFolderAsync(desiredFolderNm, CreationCollisionOption.OpenIfExists);
                        string desiredName = file.Name;
                        try
                        {
                            progress.IsActive = true;
                            this.IsEnabled = false;//disable UI
                            await file.CopyAsync(newFolder, desiredName, NameCollisionOption.FailIfExists);
                            progress.IsActive = false;
                            this.IsEnabled =true;//disable UI
                            var dialog = new MessageDialog("Upload Successfull");

                            await dialog.ShowAsync();
                        }
                        catch (Exception exp)
                        {
                            //show here messagebox that is exists
                            Windows.UI.Xaml.Controls.ContentDialog replacePromptDialog2 = new Windows.UI.Xaml.Controls.ContentDialog()
                            {
                                Title = "File exists in the new location",
                                Content = "Do you want to replace the old file with the new file?",
                                CloseButtonText = "Keep the old one",
                                PrimaryButtonText = "Replace with new one"
                            };
                            Windows.UI.Xaml.Controls.ContentDialogResult result2 = await replacePromptDialog2.ShowAsync();
                            if (result2 == Windows.UI.Xaml.Controls.ContentDialogResult.Primary)
                            {
                                await file.CopyAsync(newFolder, desiredName, NameCollisionOption.ReplaceExisting);
                            }
                        }
                    }

            }
                catch (Exception ex)
                {
                    string exx = ex.ToString();
                    var dialog = new MessageDialog(exx);
                   await dialog.ShowAsync();
                }

        }
        catch(Exception ex)
        {
                string exx = ex.ToString();
                var dialog = new MessageDialog(exx);
                await dialog.ShowAsync();
            }
            }

    }