How to use a path data from a resource dictionary in UWP - xaml

Question

This is trivial thing but yet it does not work.
I have something like this (it is in its own folder)
<ResourceDictionary>
<Path x:Key="Test"
Stroke="Black"
Fill="Gray"
Data="M 10,100 C 10,300 300,-200 300,100" />
</ResourceDictionary>
Now I want to use it
<Page>
<Page.Resources>
<ResourceDictionary>
<ResourceDictionary.MergeDictionaries>
<ResourceDictionary Source="MyFolder/MyResourceDictionary.xaml/>
</ResourceDictionary.MergeDictionaries>
</ResourceDictionary>
</Page.Resources>
<ContentPresenter Content="{StaticResource Test}"/>
<Page/>
This will throw an exception, but I don't understand why. Exactly the same scenario in wpf works fine.

Answer 1

What about this solution?
Declare your GeometryData
<x:String x:Key="TestPathGeomerty">M 10,100 C 10,300 300,-200 300,100</x:String>
And use Path, instead ContentPresenter
<Path Data="{StaticResource TestPathGeomerty}"
Fill="Red"/>

Answer 2

The Path.Data property is of type Geometry so define it as a Geometry instead of a string
<Geometry x:Key="TestPathGeomerty">M 10,100 C 10,300 300,-200 300,100</Geometry>
<Path Data="{StaticResource TestPathGeomerty}"
Fill="Red"/>

Answer 3

In WPF, you can share the same instance within multiple controls. Unfortunately this is not possible in UWP.
The only solution that is guaranteed to work in UWP, is to define a DataTemplate in your resource containing the icon.
It is also better to use PathIcon instead of Path. PathIcon makes use of the Foreground property that will be inherited from your parent controls.
Here's an example on how to share Data paths for icons that will automatically scale (by using a Viewbox).
<Page.Resources>
<DataTemplate x:Key="MagnifyingGlassPathIconCT">
<Viewbox Stretch="Uniform">
<PathIcon Data="M44,12 C32,12 22,22 22,34 22,46 32,56 44,56 56,56 66,46 66,34 66,22 56,12 44,12z M44,0 C63,0 78,15 78,34 78,53 63,68 44,68 40,68 36.5,67.5 33,66 L32.5,66 14,90 0,79.5 18,55.5 17,55 C13,49 10,42 10,34 10,15 25,0 44,0z" />
</Viewbox>
</DataTemplate>
</Page.Resources>
<StackPanel Padding="40" HorizontalAlignment="Left">
<!-- Plain icon -->
<ContentPresenter
Width="40"
Height="40"
ContentTemplate="{StaticResource MagnifyingGlassPathIconCT}"
Foreground="Purple" />
<!-- Icon with a border -->
<Border
Width="40" Padding="7"
Height="40"
BorderBrush="Black"
BorderThickness="2">
<ContentPresenter ContentTemplate="{StaticResource MagnifyingGlassPathIconCT}" Foreground="Red" />
</Border>
<!-- Icon in a normal Button -->
<Button
Width="40"
Height="40"
ContentTemplate="{StaticResource MagnifyingGlassPathIconCT}"
Foreground="RoyalBlue" />
<!-- Icon in an AppBarButton -->
<AppBarButton
Width="40"
ContentTemplate="{StaticResource MagnifyingGlassPathIconCT}"
Foreground="Black"
Label="Search" />
</StackPanel>

Answer 4

For a solution that lets you define it in a Style, try writting an attached property like this:
public static string GetPathData(DependencyObject obj)
{
return (string)obj.GetValue(PathDataProperty);
}
public static void SetPathData(DependencyObject obj, string value)
{
obj.SetValue(PathDataProperty, value);
}
public static readonly DependencyProperty PathDataProperty =
DependencyProperty.RegisterAttached("PathData", typeof(string), typeof(ElementExtensions), new PropertyMetadata(null, (d, e) =>
{
if (d is Path path)
{
Binding b = new Binding { Source = e.NewValue };
path.SetBinding(Path.DataProperty, b);
}
}));
And now you can define a style like so:
<Style x:Key="BasePathStyle" TargetType="Path">
<Setter Property="e:ElementExtensions.PathData" Value="M 10,100 C 10,300 300,-200 300,100" />
</Style>
And then use it like so:
<Path Style="{StaticResource BasePathStyle}" />