Hi Johann,

This sounds familiar, but I'm certain that it was fixed a while ago. The order the series are added to the chart determines the order they are rendered.
What's the chart framework's build number?

Can you try this code and see if you're still seeing the problem:

using MonoTouch.ObjCRuntime;
using Infragistics;

NSNumber[] data = {
    new NSNumber (4),
    new NSNumber (0),
    new NSNumber (4)
};
    
_dsh = new IGCategorySeriesDataSourceHelper (data);

_chartView = new IGChartView (this.View.Frame);

IGSeries s1 = _chartView.AddSeries(new Class("IGColumnSeries"), "series", _dsh, "x", "y");

IGSeries s2 = _chartView.AddSeries(new Class("IGLineSeries"), "series2", _dsh, "x", "y");
s2.Thickness = 5;

this.View.AddSubview (_chartView);