How can group my array data to get a stacked bar chart?

The example stacked bar chart example
https://examples4.ext.net/#/Chart/Bar/Stacked
shows exactly what I would like to get, but the example data has not the same structure as my data.

I found old sencha forum entry which has nearly the same question
https://www.sencha.com/forum/showthr...-Grouped-Store
but I am unable migrate to the fiddle solution:
http://jsfiddle.net/existdissolve/dkJb9/
to asp.net.

I found a groupField config in store but no further documentation or example if or how this config could be used with a barSeries.

To reflect my data structure, the following code is a slightly changed version of the original stacked bar chart example.
May some give me a hint how I can configure the store and the barSeries to get the same results as in the original example without changing my data structure.

thanks,
marjot

<%@ Page Language="C#" %>

<script runat="server">
    public List<object> Data
    {
        get
        {            
            return new List<object>
            {
                new { Month = "Jan", Data = 20, Browser = "IE" },
                new { Month = "Feb", Data = 20, Browser = "IE" },
                new { Month = "Mar", Data = 19, Browser = "IE" },
                new { Month = "Apr", Data = 18, Browser = "IE" },
                new { Month = "May", Data = 18, Browser = "IE" },
                new { Month = "Jun", Data = 17, Browser = "IE" },
                new { Month = "Jul", Data = 16, Browser = "IE" },
                new { Month = "Aug", Data = 16, Browser = "IE" },
                new { Month = "Sep", Data = 16, Browser = "IE" },
                new { Month = "Oct", Data = 16, Browser = "IE" },
                new { Month = "Nov", Data = 15, Browser = "IE" },
                new { Month = "Dec", Data = 15, Browser = "IE" },
                new { Month = "Jan", Data = 37, Browser = "Firefox" },
                new { Month = "Feb", Data = 37, Browser = "Firefox" },
                new { Month = "Mar", Data = 36, Browser = "Firefox" },
                new { Month = "Apr", Data = 36, Browser = "Firefox" },
                new { Month = "May", Data = 35, Browser = "Firefox" },
                new { Month = "Jun", Data = 34, Browser = "Firefox" },
                new { Month = "Jul", Data = 34, Browser = "Firefox" },
                new { Month = "Aug", Data = 33, Browser = "Firefox" },
                new { Month = "Sep", Data = 32, Browser = "Firefox" },
                new { Month = "Oct", Data = 32, Browser = "Firefox" },
                new { Month = "Nov", Data = 31, Browser = "Firefox" },
                new { Month = "Dec", Data = 31, Browser = "Firefox" },
                new { Month = "Jan", Data = 35, Browser = "Chrome" },
                new { Month = "Feb", Data = 36, Browser = "Chrome" },
                new { Month = "Mar", Data = 37, Browser = "Chrome" },
                new { Month = "Apr", Data = 38, Browser = "Chrome" },
                new { Month = "May", Data = 39, Browser = "Chrome" },
                new { Month = "Jun", Data = 42, Browser = "Chrome" },
                new { Month = "Jul", Data = 43, Browser = "Chrome" },
                new { Month = "Aug", Data = 44, Browser = "Chrome" },
                new { Month = "Sep", Data = 44, Browser = "Chrome" },
                new { Month = "Oct", Data = 45, Browser = "Chrome" },
                new { Month = "Nov", Data = 46, Browser = "Chrome" },
                new { Month = "Dec", Data = 47, Browser = "Chrome" },
                new { Month = "Jan", Data = 4,  Browser = "Safari" },
                new { Month = "Feb", Data = 5,  Browser = "Safari" },
                new { Month = "Mar", Data = 4,  Browser = "Safari" },
                new { Month = "Apr", Data = 5,  Browser = "Safari" },
                new { Month = "May", Data = 4,  Browser = "Safari" },
                new { Month = "Jun", Data = 4,  Browser = "Safari" },
                new { Month = "Jul", Data = 4,  Browser = "Safari" },
                new { Month = "Aug", Data = 4,  Browser = "Safari" },
                new { Month = "Sep", Data = 4,  Browser = "Safari" },
                new { Month = "Oct", Data = 4,  Browser = "Safari" },
                new { Month = "Nov", Data = 4,  Browser = "Safari" },
                new { Month = "Dec", Data = 4,  Browser = "Safari" },

            };
        }
    }
</script>

<!DOCTYPE html>

<html>
<head runat="server">
    <title>Stacked Bar Chart - Ext.NET Examples</title>
    <link href="/resources/css/examples.css" rel="stylesheet" />
</head>
<body>
    <form runat="server">
        <ext:ResourceManager runat="server" />

        <h1>Stacked Bar Chart Sample</h1>

        <ext:Container
            runat="server"
            Width="800"
            Height="500"
            Layout="FitLayout">
            <Items>
                <ext:CartesianChart
                    ID="Chart1"
                    runat="server"
                    FlipXY="true"
                    InsetPadding="40">
                    <Store>
                        <ext:Store runat="server" Data="<%# Data %>" AutoDataBind="true">
                            <Model>
                                <ext:Model runat="server">
                                    <Fields>
                                        <ext:ModelField Name="Month" />
                                        <ext:ModelField Name="Data" />                                        
                                    </Fields>
                                </ext:Model>
                            </Model>
                        </ext:Store>
                    </Store>

                    <LegendConfig Dock="Right" />

                    <Axes>
                        <ext:NumericAxis
                            Fields="Data"
                            Position="Bottom"                            
                            Grid="true"
                            AdjustByMajorUnit="true"
                            Minimum="0">
                        </ext:NumericAxis>

                        <ext:CategoryAxis Fields="Month" Position="Left" Grid="true" />
                    </Axes>

                    <Series>
                        <ext:BarSeries
                            XField="Month"
                            YField="Data"                            
                            Titles="IE,Firefox,Chrome,Safari"
                            Stacked="true">
                        </ext:BarSeries>
                    </Series>
                </ext:CartesianChart>
            </Items>
        </ext:Container>
    </form>
</body>
</html>