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Fun with Ink & XAML Part3: Ink Data Binding

  • Artigo

Data binding in WPF provides a great way for applications to present and interact with data. Elements can be bound to data from a variety of data sources - for example XML files. I have put together a sample that uses data binding to retrieve a collection of handwritten ink documents from a data store (XML file), present it to the user and let the user interact with it. As always in this series, the task is accomplished by markup only - no code behind required. The sample markup (and the data file) is attached to this post.

Let's take a look at the sample markup, specifically what's inside the <Grid.Resources> tag. I have highlighted the sections that are relevant for the data binding: 

<Grid.Resources>

  <XmlDataProvider x:Key="InkData" Source="inkdata.xml" XPath="InkFiles"/>

  <DataTemplate x:Key="InkDataTemplate">

    <StackPanel>

      <TextBlock HorizontalAlignment="Center" Foreground="Red"

                 Text="{Binding XPath=@FileName}"/>

      <InkPresenter HorizontalAlignment="Center"

                    LayoutTransform="0.2,0,0,0.2,0,0">

        <InkPresenter.Strokes>

          <Binding XPath="@Strokes"/>

        </InkPresenter.Strokes>

      </InkPresenter>

      <Separator/>

    </StackPanel>

  </DataTemplate>

</Grid.Resources>

The first item here is the XmlDataProvider. This class facilitates the access to XML data for data binding. The other item, our DataTemplate, defines how the data is being presented: The 'FileName' value gets assigned to a <TextBlock/> and the 'Strokes' value gets assigned to the Strokes property of an <InkPresenter/>.

To see how these two resources are being used in the actual UI markup, let's inspect the ListBox element. The ListBox is being used to display a thumbnail view of all ink documents in the data store and to let the user choose which document they want to view or edit.

<ListBox Name="lbStrokes" Background="AntiqueWhite"

ItemsSource="{Binding Source={StaticResource InkData},

XPath=InkFile}"

ItemTemplate="{StaticResource InkDataTemplate}"/>

Now to view and interact with the selected item from our ListBox, we are adding a larger InkCanvas element that is data-bound to the ListBox. So when the user selects a new ink note from the list, that document gets loaded into the InkCanvas automatically. Here is the relevant markup to set up that binding:

<InkCanvas DataContext="{Binding ElementName=lbStrokes,Path=SelectedItem}"

Strokes="{Binding XPath=@Strokes}"

Background="Snow">

Below is a screenshot of the sample that is attached to this post. To run it, unpack the .zip file and load the .xaml file into XamlPad - or just double-click it to open it in IE. Note that the data file (InkData.xml) must reside in the same location as the XAML file.

Ink Data Binding Sample in XamlPad

Next post in this series: Fun with Ink & XAML Part4: WPF BitmapEffects applied to Ink

Previous post in this series: Fun with Ink & Xaml - Part2: Zoom and Scroll

InkDataBinding.zip

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