Selecting a certain row from a dataset

Question

Hi, I have a Dataset and want to display the containing rows in a WPF-Contorl. The problem is, that the control is sort of a circuit diagram. Thus I created a template to show the values and placed multiple instances of it in my circuit control. Currently the XAML-code in the circuit looks like this:

<Label Content="{Binding Path=.[0]}" ContentTemplate="{StaticResource ValueTpl}" />
<Label Content="{Binding Path=.[1]}" ContentTemplate="{StaticResource ValueTpl}" />

And so on. So I'm able to show the n-th row at a specified position. The problem is, that I can't expect the right order anymore and I would rather need something like:

<Label Content="{Binding Path=.[id=5]}" ContentTemplate="{StaticResource ValueTpl}" />
<Label Content="{Binding Path=.[id=8]}" ContentTemplate="{StaticResource ValueTpl}" />

I read that XPath ought to be supported, but I can't get this to work.

Answer 1

It is supported if you type XPath instead of Path...

Answer 2

Yes, I need to use XPath, but there's more to it.
My mistakes were:
You can't use a DataSet directly but need to wrap it in a XmlDataDocument
Also my problem involved the namespaces. To surpress them you have to set DataSet.Namespace = String.Empty prior to creating the XmlDataDocument.
If you want to use Namespaces you have to create a XmlNamespaceMappingCollection in XAML like this

<UserControl.Resources>
    <XmlNamespaceMappingCollection x:Key="namespace">
        <XmlNamespaceMapping Prefix="ds" Uri="http://tempuri.org/DataSet.xsd" />
    </XmlNamespaceMappingCollection>
</UserControl.Resources>

In order to reference the namespace in the XPath. Simply adding it as xmlns won't work (as opposed to what I expected).
Then referencing a certain row worked like this:

<Label Content="{Binding XPath='//TableName[4]'}" />

If you use namespaces, you need to reference the XmlNamespaceManager

<Label Content="{Binding XPath='//ds:TableName[4]'}" Binding.XmlNamespaceManager="{StaticResource namespace}" />

Now while this very simple XPath works, adding a constraint will lead to full CPU usage and my program not continuing:

<Label Content="{Binding XPath='//TableName[Process = 4]'}" />
or
<Label Content="{Binding XPath='//ds:TableName[ds:Process = 4]'}" Binding.XmlNamespaceManager="{StaticResource namespace}" />

EDIT It seems like the binding must be in OneTime Mode. Simply changing it to

<Label Content="{Binding Mode=OneTime, XPath='//TableName[Process = 4]'}" />

made it work. I also use a ContentTemplate and in the template the binding might be TwoWay, but there the XPath is primitive (e.g. ./Prozess) , maybe thats why.