How to display Icon in the ToolBar menu on UWP using markup extension

Hi, I am using markup extension developed by ( @NMackay ) to display images on android and uwp platform.
Everything works fine in xaml, however now I need to display icon in toolbar in UWP app (which is working fine in Android).
I need to know how can I refer this extension in my code C# code.

      var toolbarItem = new ToolbarItem
      {
        Text = "ABC",
        Order = ToolbarItemOrder.Primary,
        Icon = "search.png", **//How to refer extension to display this icon**
        Command = viewModel.MysearchCommand
      };

I am copy & pasting the extension here, since right now I cant post the links in this forum.

public class PlatformImageExtension : IMarkupExtension<string>
{

    public string SourceImage { get; set; }

    public string ProvideValue(IServiceProvider serviceProvider)
    {
        if (SourceImage == null)
            return null;

        string imagePath;
        switch (Device.RuntimePlatform)
        {
            case Device.Android:
                imagePath = SourceImage;
                break;
            case Device.iOS:
                imagePath = SourceImage + ".png";
                break;
            case Device.WinPhone:
                imagePath = "Images/" + SourceImage + ".png";
                break;
            case Device.Windows:
                imagePath = "Images/" + SourceImage + ".png";
                break;
            default:
                throw new ArgumentOutOfRangeException();
        }
        return imagePath;
    }

    object IMarkupExtension.ProvideValue(IServiceProvider serviceProvider)
    {
        return ProvideValue(serviceProvider);
    }
}