Having the following XAML, doing itListViewCategories.MouseDoubleClick += MouseDoubleClickFunction;

MouseDoubleClickFunction is not called anymore while double clicking.

   <Grid Grid.Row="1">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="Auto"/>
        </Grid.ColumnDefinitions>
        <!-- COL 0 - LEFT PANEL             -->
        <Grid Grid.Column="0" VerticalAlignment="Stretch">
            <StackPanel x:Name="itGridViewLeft" Orientation="Vertical">

            </StackPanel>
        </Grid>

        <!-- COL 1 - CENTER                 -->
        <Grid x:Name="itGridViewCenter" Grid.Column="1" VerticalAlignment="Stretch">

        </Grid>

        <!-- COL 2 - RIGHT PANEL            -->
        <Grid Grid.Column="2" HorizontalAlignment="Left" VerticalAlignment="Top" ScrollViewer.VerticalScrollBarVisibility="Visible">
            <ScrollViewer>
                <StackPanel x:Name="itGridViewRight" VerticalAlignment="Top">

<Grid Width="400" ScrollViewer.VerticalScrollBarVisibility="Visible">
<Expander Header="{StaticResource locCategories}" ExpandDirection="Down" IsExpanded="False">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>

        <Grid Grid.Row="0">
            <TextBox x:Name="itTextBoxFilter" Grid.Row="0" HorizontalAlignment="Stretch" VerticalAlignment="Top" Height="Auto"></TextBox>
            <TextBlock VerticalAlignment="Center" Foreground="#22FFFFFF" Text="{StaticResource locFilter}" Margin="5,0,0,0" IsHitTestVisible="False"/>
        </Grid>

            <ListView Grid.Row="1" x:Name="itListViewCategories" SelectionMode="Single" ScrollViewer.VerticalScrollBarVisibility="Visible">
            <ListView.ContextMenu>
                <ContextMenu>
                    <MenuItem x:Name="itContextSelectAll" Header="Select All"></MenuItem>
                    <MenuItem x:Name="itContextUnselectAll" Header="UnSelect All"></MenuItem>
                </ContextMenu>
            </ListView.ContextMenu>
            <ListView.View>
                <GridView>
                    <GridView.ColumnHeaderContainerStyle>
                        <Style>
                            <Setter Property="FrameworkElement.Visibility"  Value="Collapsed"/>
                            <Setter Property="FrameworkElement.Height" Value="1"/>
                        </Style>
                    </GridView.ColumnHeaderContainerStyle>
                    <GridViewColumn>
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <CheckBox x:Name="itCheckBoxList" Margin="0" VerticalAlignment="Center" IsChecked="{Binding IsChecked}" Checked="OnCheck" Unchecked="OnCheck"></CheckBox>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                    <GridViewColumn>
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <TextBlock Margin="0" Text="{Binding Text}"></TextBlock>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                    <GridViewColumn>
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <Ellipse Fill="{Binding ColorBrush}" Width="20" Height="20" MouseEnter="Ellipse_MouseEnter" MouseLeave="Ellipse_MouseLeave" Stroke="#55FFFFFF" MouseLeftButtonDown="Ellipse_MouseLeftButtonDown" StrokeThickness="1">
                                    <!-- <Ellipse.Style>
                                        <Style TargetType="Ellipse">
                                            <Setter Property="Stroke" Value="Black"/>
                                            <Style.Triggers>
                                                <Trigger Property="IsMouseOver" Value="True">
                                                    <Setter Property="Width" Value="20"/>
                                                </Trigger>
                                            </Style.Triggers>
                                        </Style>
                                    </Ellipse.Style>-->
                                </Ellipse>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                </GridView>
            </ListView.View>
        </ListView>
        </Grid>
    </Expander>
</Grid>
                </StackPanel>
            </ScrollViewer>
        </Grid>

    </Grid>