problem with Composition 2 colors to LinearGradientBrush in windows phone

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Windows-Phone-8

Hi i want to change my button background to 2 colors and i wrote code for it but it just add second color how can i Composition more than 2 colors
and this is my code

LinearGradientBrush lgb = new LinearGradientBrush();
GradientStop st = new GradientStop();
st.Offset = 0.1;
st.Color = Colors.Green;
GradientStop st2 = new GradientStop();
st.Offset = 1.0;
st.Color = Colors.Orange;
lgb.GradientStops.Add(st);
lgb.GradientStops.Add(st2);
btnClick.Background = lgb;

With Respectٌ