This is perhaps the simplest way of going about it:

Xaml:

<UserControl x:Class="SilverlightApplication144.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400"
             xmlns:igChart="http://schemas.infragistics.com/xaml"
             xmlns:local="clr-namespace:SilverlightApplication144">
    <UserControl.Resources>
        <local:TestData x:Key="data" />
        
        <DataTemplate x:Name="textMarker">
            <TextBlock Text="{Binding Item.Value}" Margin="0,-20,0,0" />
        </DataTemplate>
    </UserControl.Resources>

    <Grid x:Name="LayoutRoot" Background="White">
        <igChart:XamDataChart x:Name="theChart">
            <igChart:XamDataChart.Axes>
                <igChart:NumericYAxis x:Name="yAxis" MinimumValue="0" MaximumValue="10" />
                <igChart:CategoryXAxis 
                    x:Name="xAxis"
                    ItemsSource="{StaticResource data}"
                    Label="{}{Label}"/>
            </igChart:XamDataChart.Axes>
            <igChart:XamDataChart.Series>
                <igChart:ColumnSeries
                    x:Name="series"
                    MarkerTemplate="{StaticResource textMarker}"
                    ItemsSource="{StaticResource data}"
                    XAxis="{Binding ElementName=xAxis}"
                    YAxis="{Binding ElementName=yAxis}"
                    ValueMemberPath="Value" />
            </igChart:XamDataChart.Series>
        </igChart:XamDataChart>
    </Grid>
</UserControl>

And code behind

 public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
        }
    }

    public class TestData
        : ObservableCollection<TestDataItem>
    {
        public TestData()
        {
            Add(new TestDataItem()
            {
                Label = "A",
                Value = 1
            });
            Add(new TestDataItem()
            {
                Label = "B",
                Value = 2
            });
            Add(new TestDataItem()
            {
                Label = "C",
                Value = 3
            });
            Add(new TestDataItem()
            {
                Label = "D",
                Value = 4
            });
        }
    }

    public class TestDataItem
    {
        public string Label { get; set; }
        public double Value { get; set; }
    }	

Hope this helps!
-Graham