not sure what I am doing wrong but the font size isn't changing.
color and font type and italics and underline seem ok but not the size. (I removed it from here)
it stays the same real small font, 8 maybe.
here is the code...
IAutoShape generalInfo = slide.Shapes.AddAutoShape(ShapeType.Rectangle, leftMargin, topMargin, columnWidth, rowHeight);
generalInfo.FillFormat.FillType = FillType.Solid;
generalInfo.FillFormat.SolidFillColor.Color = Color.Transparent;
ITextFrame gitf = generalInfo.TextFrame;
gitf.Text = "test text";
IPortion port0 = gitf.Paragraphs[0].Portions[0];
port0.PortionFormat.FontHeight = 20;