You would need to change the code in the sample to

            List<NSString> valueList = new List<NSString> ();
            valueList.Add (new NSString("Value1"));
            valueList.Add (new NSString("Value2"));
            valueList.Add (new NSString("Value3"));

            _stackedChartDataSourceHelper = new IGStackedSeriesDataSourceHelper(  _data.ToArray(), 
                                                                               
                                                                             
                                                                                valueList.ToArray());

and add the following #usings

using Infragistics;
using System.Collections.Generic;
using MonoTouch.ObjCRuntime;

attached is the .cs class with the changes

Thanks for your help! 

now i have this code and it's almost done!  

3 more things:

 -> i need to change the items name...is showing "item 0" and "item 1"

-> i would like to put the numeric data like "10k"

-> and how i change de font colour of the theme?

thanks for you help

public void ConstroiGraficoLoanAdvisor()
        {    
            this.PopulateData();

            _chartView = new IGChartView();
            _chartView.Theme = IGChartGradientThemes.FinanceTheme2();
            _chartView.Theme.LegendFont = UIFont.FromName("Helvetica Neue", 9);
            _chartView.Theme.Font = UIFont.FromName("Helvetica Neue", 9);
            _chartView.Frame = new RectangleF (5, 6, 240, 155);
            _chartView.BackgroundColor = UIColor.LightGray;
            _chartView.AutoresizingMask = UIViewAutoresizing.FlexibleHeight | UIViewAutoresizing.FlexibleWidth;

            _chartView.Delegate = new SampleChartDelegate(); 



            List<NSString> valueList = new List<NSString> ();
            valueList.Add (new NSString("Interests"));
            valueList.Add (new NSString("Principal"));
            valueList.Add (new NSString("Costs"));


            _stackedChartDataSourceHelper = new IGStackedSeriesDataSourceHelper(_data.ToArray(),valueList.ToArray());



            IGNumericXAxis xAxis = new IGNumericXAxis("xAxis");
            xAxis.LabelOrientationAngle = -90;
            xAxis.Extent = 50;


            IGCategoryYAxis yAxis = new IGCategoryYAxis("yAxis");
            yAxis.IsInverted = true;
            _chartView.AddAxis(xAxis);
            _chartView.AddAxis(yAxis);


            IGStackedBarSeries series = new IGStackedBarSeries ("series");
            series.XAxis = xAxis;
            series.YAxis = yAxis;



            series.DataSource = _stackedChartDataSourceHelper;


            _chartView.AddStackedSeries(new Class(typeof(IGStackedBarSeries)), "series", _stackedChartDataSourceHelper, "xAxis", "yAxis");


            (this.View).AddSubview(_chartView);


            _legend = new IGLegend(IGChartLegendType.IGChartLegendTypeSeries);
            _legend.Frame = new RectangleF(240, 10, 70, 60);
            _chartView.Legend = _legend;


            (this.View).AddSubview(_legend);
        }


        void PopulateData()
        {
            _data = new List<NSObject>();

            DataModel item = new DataModel();

            item.Interests = wOutputValorJurosLoanInput;
            item.Principal = wOutputValorAmortizacaoLoanInput;
            item.Costs = wOutputValorOutrosCustosLoanInput;
            item.Label = string.Format ("A");

            _data.Add (item);


            item = new DataModel();

            item.Interests = wOutputValorJurosLoanAdvisor;
            item.Principal = wOutputValorAmortizacaoLoanAdvisor;
            item.Costs = wOutputValorOutrosCustosLoanAdvisor;
            item.Label = "Advise";  

            _data.Add (item);

        }


        public class DataModel : NSObject
        {
            [Export("Label")]
            public string Label { get; set; }
            [Export("Interests")]
            public float Interests { get; set; }
            [Export("Principal")]
            public float Principal { get; set; }
            [Export("Costs")]
            public float Costs { get; set; }
        }

Hi,

thanks for you answer, now it's working!

You would not be able to change the theme values, as they are read only.  

you can set the axis labelBrush property to a new IGBrush for that axis.

            // sets the X-Axis labels to be red 
            IGStackedBarSeries s = (IGStackedBarSeries)_chartView.Series [0];
            s.XAxis.LabelBrush = new IGBrush (UIColor.Red);

As for custom labels,you would need to attach a delegate (and by extension create a delegate handler) to the IGChartView and process on the ResolveLabelForAxis method call in order to return your custom labels. 

Updated the code file to show these changes.