Dependent databinds (series of combos)

I have an app with a series of combo boxes. The general idea is that you
select the first one, and that creates a parameter that feeds the next
combo, and so forth. They're all fed from a single XML datasource, and I
have no problem feeding the first combo. What I'm hung up on is how to have
the selection of the first trigger the 2nd combo to rebind using hte
parameter from the first in the XPath for the 2nd. Is this possible just in
markup, or do I need to tie the combos together via in-code event handlers?

Hi,

Keith Patrick wrote:
> I have an app with a series of combo boxes. The general idea is that you
> select the first one, and that creates a parameter that feeds the next
> combo, and so forth. They're all fed from a single XML datasource, and I
> have no problem feeding the first combo. What I'm hung up on is how to have
> the selection of the first trigger the 2nd combo to rebind using hte
> parameter from the first in the XPath for the 2nd. Is this possible just in
> markup, or do I need to tie the combos together via in-code event handlers?

I thought it over and so far I don't see a solution with markup only.
Event handling is probably the one functionality where code-behind is
pretty much irreplacable. Is it a big problem for you to use code-behind?

Greetings,
Laurent
--
Laurent Bugnion, GalaSoft
Software engineering: http://www.galasoft-LB.ch
PhotoAlbum: http://www.galasoft-LB.ch/pictures
Support children in Calcutta: http://www.calcutta-espoir.ch

Hi,

Keith Patrick wrote:
> I have an app with a series of combo boxes. The general idea is that you
> select the first one, and that creates a parameter that feeds the next
> combo, and so forth. They're all fed from a single XML datasource, and I
> have no problem feeding the first combo. What I'm hung up on is how to have
> the selection of the first trigger the 2nd combo to rebind using hte
> parameter from the first in the XPath for the 2nd. Is this possible just in
> markup, or do I need to tie the combos together via in-code event handlers?

I thought it over and so far I don't see a solution with markup only.
Event handling is probably the one functionality where code-behind is
pretty much irreplacable. Is it a big problem for you to use code-behind?

Greetings,
Laurent
--
Laurent Bugnion, GalaSoft
Software engineering: http://www.galasoft-LB.ch
PhotoAlbum: http://www.galasoft-LB.ch/pictures
Support children in Calcutta: http://www.calcutta-espoir.ch

Only problem I've been having is explicitly refreshing the datasource. I've
tried XmlDataProvider.Refresh() as well as XmlDataProvider.InitialLoad(),
but they won't update, so I was hoping to let the underlying runtime do
whatever it does the correct way to get the data updated.

Only problem I've been having is explicitly refreshing the datasource. I've
tried XmlDataProvider.Refresh() as well as XmlDataProvider.InitialLoad(),
but they won't update, so I was hoping to let the underlying runtime do
whatever it does the correct way to get the data updated.

It looks like I can do this declaratively using MultiBindings (the first
binding is to the XML, and the additional ones are for each combobox the
declared combo's filtering depends on). The only code I have to write is a
custom IMultiValueConverter to take the SelectedValues from the bindings &
do a String.Format with them & the XPath

It looks like I can do this declaratively using MultiBindings (the first
binding is to the XML, and the additional ones are for each combobox the
declared combo's filtering depends on). The only code I have to write is a
custom IMultiValueConverter to take the SelectedValues from the bindings &
do a String.Format with them & the XPath

Multibindings are actually overkill here. This is my solution, whereby the
combos all just talk in XML, such that the dependent relationship is
implicit in the hierarchical structure of the source XML. Any further
dependencies would then depend on ChildCombo, GrandChildCombo, etc.:

<StackPanel>
<ComboBox Name="ParentCombo"
ItemsSource="{Binding Source={StaticResource
XmlSource}, XPath=//Root/Parents/Parent}"
ItemTemplate="{StaticResource NamedXmlControl}"/>
<ComboBox Name="ChildCombo"
ItemsSource="{Binding ElementName=ParentCombo,
Path=SelectedItem, XPath=Children/Child}"
ItemTemplate="{StaticResource NamedXmlControl}"/>
</StackPanel>

where
<DataTemplate x:Key="NamedXmlControl">
<TextBlock Text="{Binding XPath=@Name}"/>
</DataTemplate>
<XmlDataProvider x:Key="XmlSource" .../>

Multibindings are actually overkill here. This is my solution, whereby the
combos all just talk in XML, such that the dependent relationship is
implicit in the hierarchical structure of the source XML. Any further
dependencies would then depend on ChildCombo, GrandChildCombo, etc.:

<StackPanel>
<ComboBox Name="ParentCombo"
ItemsSource="{Binding Source={StaticResource
XmlSource}, XPath=//Root/Parents/Parent}"
ItemTemplate="{StaticResource NamedXmlControl}"/>
<ComboBox Name="ChildCombo"
ItemsSource="{Binding ElementName=ParentCombo,
Path=SelectedItem, XPath=Children/Child}"
ItemTemplate="{StaticResource NamedXmlControl}"/>
</StackPanel>

where
<DataTemplate x:Key="NamedXmlControl">
<TextBlock Text="{Binding XPath=@Name}"/>
</DataTemplate>
<XmlDataProvider x:Key="XmlSource" .../>