“无法将字符串转换为ImageSource。”我该怎么做？

private void HeroMouseEnter(object sender, MouseEventArgs e)
    {
        ((Image)sender).Source = GetGlowingImage(((Image)sender).Name);            
    }

    public ImageSource GetGlowingImage(string name)
    {
        switch (name)
        {
            case "Andromeda":
                return "HeroGlowIcons/64px-Andromeda.gif";                
            default:
                return null;
        }
    }
private void HeroMouseEnter(object sender, Mous