What reference do I need to add to a Windows Store app to use the Bitmap class?

See more:

C#5.0

Bitmap

Windows-Store

I need to use a Bitmap class in my app, but this code:

public class PushpinMetadata
{
    public string FileName { get; set; }
    public DateTime DateTimeTaken { get; set; }
    public Bitmap thumbnail { get; set; }
}

...fails because "Bitmap" cannot be found. What reference do I need to add to my project for Bitmap to be resolvable?

Or do I need something else - Picture? Image? Or...???

This is a Windows Store app (Windows 8.1)