Presentation ppt = new Presentation();
IChart chart = ppt.Slides[0].Shapes.AppendChart(ChartType.Line, new RectangleF(50, 100, 400, 400));
chart.PrimaryValueAxis.ChartCrossType = ChartCrossesType.AxisCrossesAtZero;
chart.ChartTitle.TextProperties.Text = ChartCrossesType.Custom.ToString();
chart.HasTitle = true;
//a serie on a secondary(value) axis
chart.Series[0].UseSecondAxis = true;
ppt.SaveToFile("result.pptx", FileFormat.Pptx2010);