XAML Tool Tip Data Context and Multi Binding - wpf

Question

I have a ListView in my XAML and I am trying to hook up a MultiBinding Converter.
<ListView
Grid.Column="4"
Grid.Row="1"
Grid.RowSpan="5"
Margin="8,0,8,8"
HorizontalAlignment="Stretch"
Name="lvDisplayType"
ItemsSource="{Binding Path=Types}"
SelectedItem="{Binding Path=Current.Opt}"
VerticalAlignment="Stretch"
SelectionChanged="lvType_SelectionChanged"
SelectionMode="Single"
ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListView.ItemTemplate>
<DataTemplate>
<DockPanel
HorizontalAlignment="Center">
<TextBlock
Text="{Binding Path=., Converter={StaticResource DisplayConverter}}"
HorizontalAlignment="Center"
Padding="6"
VerticalAlignment="Center"
TextWrapping="Wrap">
<TextBlock.ToolTip>
<ToolTip DataContext="{Binding Path=Current}">
<MultiBinding Converter="{StaticResource OptConverter}">
<Binding Path="Opt" />
<Binding Path="Type" />
</MultiBinding>
</ToolTip>
</TextBlock.ToolTip>
</TextBlock>
</DockPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
The code not working is:
<TextBlock.ToolTip>
<ToolTip DataContext="{Binding Path=Current}">
<MultiBinding Converter="{StaticResource OptConverter}">
<Binding Path="Opt" />
<Binding Path="Type" />
</MultiBinding>
</ToolTip>
</TextBlock.ToolTip>
At present the Converter is returning an empty string as both 'values[0] == System.Windows.DependencyProperty.UnsetValue' and 'values[1] == System.Windows.DependencyProperty.UnsetValue' return true. These values are never set.
Because of the logical tree (I think) the TextBlock.ToolTip default binding is 'Current.Opt'. For the MultiBinding I also need to refer to 'Type' which is another property of 'Current'. So to get around this I have set 'ToolTip DataContext="{Binding Path=Current}"' - this isn't working as expected - what am I doing wrong?
I know I could do this easily in the Code behind, but we are employing MVVM, so would like to avoid it if possible.
Any help greatly appreciated!
Thank you

Answer 1

Try to do it in this way,
1.Does this give DependencyProperty.UnsetValue in the Converter? Otherwise, what is coming in to the converter?
<TextBlock.ToolTip>
<MultiBinding Converter="{StaticResource OptConverter}">
<Binding RelativeSource="{RelativeSource Self}" />
<Binding RelativeSource="{RelativeSource Self}" />
</MultiBinding>
</TextBlock.ToolTip>
2.Does this give DependencyProperty.UnsetValue in the Converter?
<TextBlock.ToolTip>
<MultiBinding Converter="{StaticResource OptConverter}">
<Binding RelativeSource="{RelativeSource Self}" Path="Current"/>
<Binding RelativeSource="{RelativeSource Self}" Path="Current"/>
</MultiBinding>
</TextBlock.ToolTip>