the codes like this:

 class cExDataNode
        {
            private object f_val;

            public object F_val
            {
                get { return f_val; }
                set { f_val = value; }
            }
            private DateTime dtm;

            public DateTime Dtm
            {
                get { return dtm; }
                set { dtm = value; }
            }

        }
        List<cExDataNode> ls_rownodes;

        private void OnSampleLoaded(object sender, RoutedEventArgs e)
        {
            DateTime tm = DateTime.Now;
            ls_rownodes = new List<cExDataNode>();
            for (int i = 0; i < 100; i++)
            {
                cExDataNode dp = new cExDataNode();
                dp.Dtm = tm.AddSeconds(i);
                dp.F_val = i * 10;
                ls_rownodes.Add(dp);
            }

            ls_rownodes[0].F_val = 0;
            ls_rownodes[1].F_val = 0;
            ls_rownodes[2].F_val = 0;
            ls_rownodes[3].F_val = null;
            ls_rownodes[4].F_val = null;
            ls_rownodes[5].F_val = 0;
            ls_rownodes[6].F_val = 0;
            ls_rownodes[7].F_val = 0;
            ls_rownodes[8].F_val = 0;
            ls_rownodes[9].F_val = 0;
            ls_rownodes[10].F_val = 0;
            ls_rownodes[90].F_val = null;

            this.DataContext = ls_rownodes;

        }

 <ig:XamDataChart x:Name="DataChart">
            <ig:XamDataChart.Axes>
                <ig:CategoryDateTimeXAxis x:Name="categoryXAxis" ItemsSource="{Binding}" Label="{}{Dtm:hh:mm:ss.fff}" DateTimeMemberPath="Dtm"
                                               DisplayType="Continuous">
                    <ig:CategoryDateTimeXAxis.LabelSettings>
                        <ig:AxisLabelSettings Location="OutsideBottom" Extent="45" VerticalAlignment="Center" Visibility="Visible" />
                    </ig:CategoryDateTimeXAxis.LabelSettings>
                </ig:CategoryDateTimeXAxis>
                <ig:NumericYAxis x:Name="numericYAxis" Label="{}{:F1}">
                    <ig:NumericYAxis.LabelSettings>
                        <ig:AxisLabelSettings Location="OutsideLeft" Extent="60" Visibility="Visible" />
                    </ig:NumericYAxis.LabelSettings>
                </ig:NumericYAxis>
            </ig:XamDataChart.Axes>
            <ig:XamDataChart.Series>
                <ig:LineSeries  ValueMemberPath="F_val" MarkerType="None" ItemsSource="{Binding}"  XAxis="{Binding ElementName=categoryXAxis}" YAxis="{Binding ElementName=numericYAxis}" Thickness="2.5" UnknownValuePlotting="LinearInterpolate">
                </ig:LineSeries>
            </ig:XamDataChart.Series>
        </ig:XamDataChart>

and the result:

 ???, the infargistics SL DV ver is 11.2 trial