Text Alignment with SpannableString

Referencing this post I've tried to use a SpannableString to align items within a TextView:

var rightLeft = "right left";
            var spanString = new SpannableString(rightLeft);
            spanString.SetSpan(new AlignmentSpanStandard(Layout.Alignment.AlignOpposite), 5, 
rightLeft.Length, SpanTypes.ExclusiveExclusive);
            spanString.SetSpan(new AlignmentSpanStandard(Layout.Alignment.AlignNormal), 0, 5, 
SpanTypes.ExclusiveExclusive);
            var tv2 = new TextView(this);
            tv2.LayoutParameters = new ViewGroup.LayoutParams(400, 100);

Any suggestions?