Different datacontext between textbox and its tooltip in silverlight

Question

I'm trying to do something apparently easy but I don't know why is not working.

This works fine:

<TextBox DataContext="{Binding ElementName=CORDONES_ESTATALESDomainDataSource, Path=Data}" Text="{Binding Path=DNA_A1}">
    <ToolTipService.ToolTip>
        <ToolTip Content="{Binding Path=DNA_A1}"/>
    </ToolTipService.ToolTip>
</TextBox>

I'm showing the same content in the tooltip than in the textbox. On the contrary:

<TextBox DataContext="{Binding ElementName=CORDONES_ESTATALESDomainDataSource, Path=Data}" Text="{Binding Path=DNA_A1}">
    <ToolTipService.ToolTip>
        <ToolTip DataContext="{Binding ElementName=TIPAJES_INTERMEDIOSDomainDataSource, Path=Data}" Content="{Binding Path=ALELOS_DNA_A2}"/>
    </ToolTipService.ToolTip>
</TextBox>

This shows nothing. Note that the only change is that the tooltip has a different DataContext because the domaindatasource is also different.

Why is this happening? Am I doing something wrong or is it impossible to do? Is it because the different datacontexts? If this is not the way, how can I do this?

Thanks

Answer 1

I didn't find a way to do it work so I solved the following way.

<TextBox DataContext="{Binding ElementName=CORDONES_ESTATALESDomainDataSource, Path=Data}" Text="{Binding Path=DNA_A1}">
<ToolTipService.ToolTip>
    <ToolTip Name="DNA_A1Tooltip" Content=""/>
</ToolTipService.ToolTip>

I set the content to "" and I assign the tooltip a name. Then in the currentChanged event of the domain datasource I assign programaticaly the value its content:

DNA_A1Tooltip.Content = TIPAJES_INTERMEDIOSDomainDataSource.DataView.CurrentItem.ALELOS_DNA_A1()

I know it's not the most elegant solution but it works.