I use multi Series,first one is lineSeries and second one is PointSeries.
I set on some points a custom Tooltip and others that have no content to display in Tooltip. Now i want to hide that Tooltip has no content

<ig:XamDataChart x:Name="DataChart" Height="314" Width="707" 
                         HorizontalAlignment="Stretch"
                         VerticalAlignment="Stretch"
                         IsHorizontalZoomEnabled="True" 
                         VerticalZoombarVisibility="Visible"
                         DockPanel.Dock="Right"
                         HorizontalZoomable="True"
                         PlotAreaBackground="Transparent"
                         CrosshairVisibility="Visible"
                         Background="Transparent"
                         VerticalZoomable="True"
                         ToolTipStyle="{StaticResource ToolTipStyle}">
            <ig:XamDataChart.Resources>

            </ig:XamDataChart.Resources>
            <ig:XamDataChart.Axes>
                <ig:CategoryDateTimeXAxis x:Name="XmXAxis" 
                             DateTimeMemberPath="Date" 
                             ItemsSource="{Binding Weathers}" 
                             Label="{}{Date:dd MMM}">
                </ig:CategoryDateTimeXAxis>
                <ig:NumericYAxis x:Name="volumeYAxis" Opacity="0" MinimumValue="0" MaximumValue="10" Interval="1">
                    <ig:NumericYAxis.LabelSettings>
                        <ig:AxisLabelSettings Visibility="Collapsed"></ig:AxisLabelSettings>
                    </ig:NumericYAxis.LabelSettings>
                </ig:NumericYAxis>
                <ig:NumericYAxis x:Name="yAxis" MinimumValue="0" MaximumValue="10" Interval="1" >
                </ig:NumericYAxis>
            </ig:XamDataChart.Axes>
            <ig:XamDataChart.Series>
                <ig:LineSeries 
                   MarkerType="Square"
                   ItemsSource="{Binding Path=Weathers}"
                   ValueMemberPath="temp"
                   XAxis="{Binding ElementName=XmXAxis}"
                   YAxis="{Binding ElementName=volumeYAxis}">
                </ig:LineSeries>
                <ig:PointSeries  x:Name="Series1" 
                               XAxis="{Binding ElementName=XmXAxis}" 
                               YAxis="{Binding ElementName=yAxis}" 
                               Thickness="2" 
                               Brush="Blue" 
                               MarkerType="Circle"
                               ItemsSource="{Binding Path=Tests}"
                               ValueMemberPath="Yaxiss"
                               >

                    <ig:PointSeries.ToolTip >
                        <igDP:XamDataGrid DataSource="{Binding Path=Item.TestComments}"
                                              Theme="RoyalLight"
                                              Width="Auto"
                                              Height="Auto" >
                            <igDP:XamDataGrid.FieldLayoutSettings>
                                <igDP:FieldLayoutSettings AutoGenerateFields="False" />
                            </igDP:XamDataGrid.FieldLayoutSettings>
                            <igDP:XamDataGrid.FieldSettings>
                                <igDP:FieldSettings AllowEdit="True" IsAutoEditModeEnabled="True" CellClickAction="SelectCell" />
                            </igDP:XamDataGrid.FieldSettings>
                            <igDP:XamDataGrid.FieldLayouts>
                                <igDP:FieldLayout>
                                    <igDP:Field Name="username"/>
                                    <igDP:Field Name="Comment"/>
                                </igDP:FieldLayout>
                            </igDP:XamDataGrid.FieldLayouts>
                        </igDP:XamDataGrid>
                    </ig:PointSeries.ToolTip>
                    <ig:PointSeries.MarkerTemplate>
                        <DataTemplate>
                            <Canvas Name="g862">
                                <Canvas.RenderTransform>
                                    <MatrixTransform Matrix="0.03479732 0 0 0.03479732 1.1126985 1.2357275"/>
                                </Canvas.RenderTransform>
                                <Canvas Name="g860">
                                    <Path xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Name="path858" Fill="#000000">
                                        <Path.Data>
                                            <PathGeometry Figures="M 256 0 C 114.844 0 0 114.844 0 256 0 397.156 114.844 512 256 512 397.156 512 512 397.156 512 256 512 114.844 397.156 0 256 0 Z m 42.667 416 c 0 5.896 -4.771 10.667 -10.667 10.667 h -64 c -5.896 0 -10.667 -4.771 -10.667 -10.667 V 256 h -10.667 c -5.896 0 -10.667 -4.771 -10.667 -10.667 v -42.667 c 0 -5.896 4.771 -10.667 10.667 -10.667 H 288 c 5.896 0 10.667 4.771 10.667 10.667 z M 256 170.667 c -23.531 0 -42.667 -19.135 -42.667 -42.667 0 -23.532 19.136 -42.667 42.667 -42.667 23.531 0 42.667 19.135 42.667 42.667 0 23.532 -19.136 42.667 -42.667 42.667 z" FillRule="NonZero"/>
                                        </Path.Data>
                                    </Path>
                                </Canvas>
                            </Canvas>
                        </DataTemplate>
                    </ig:PointSeries.MarkerTemplate>
                </ig:PointSeries>

            </ig:XamDataChart.Series>
        </ig:XamDataChart>