How to retrieve png image from SpecialFolder.LocalApplicationData and show on UI as button.Image ?

I'm sending image by TCP and save on SpecialFolder.LocalApplicationData. Next I want to retrieve this image and show as button.Image in runtime,
but the image doesn't show, only empty button.

`button.Data.ThumbnailPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.LocalApplicationData) + // + fileName;

if (File.Exists(button.Data.ThumbnailPath))
{
button.Image = (FileImageSource)ImageSource.FromFile(button.Data.ThumbnailPath);
MainGrid.Children.Add(button, 0, 0);
}`