Only last icon in XAML shown when icon used from resources - wpf

Question

when I try to use a material design icon from the icon pack that is defined in the ResourceDictionary, only the first icon in XAML is rendered at run time. I've followed an example that can be found here.
Example follows:
App.xaml:
<Application x:Class="TestWpf.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:TestWpf"
xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
StartupUri="MainWindow.xaml">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<materialDesign:BundledTheme BaseTheme="Light" PrimaryColor="DeepPurple" SecondaryColor="Lime" />
<ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.Defaults.xaml" />
<ResourceDictionary Source="pack://application:,,,/TestWpf;component/Dictionary1.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
Dictionary1.xaml:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes">
<materialDesign:PackIcon x:Key="CashIcon" Kind="Cash" />
</ResourceDictionary>
MainWindow.xaml:
<Window x:Class="TestWpf.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="450" Width="800">
<StackPanel>
<Button Content="{DynamicResource CashIcon}" />
<Button Content="{DynamicResource CashIcon}" />
<Button Content="{DynamicResource CashIcon}" />
</StackPanel>
</Window>
And the result is a window that looks like this:
In xaml editor all buttons have icons on them, as expected:
Why is this happening and, more important, how to fix this?
P.S. We've found out that if you create two Cash icons in the ResourceDictionary and apply each to a button, then they will both be shown but again, only once, you can't have say 3 buttons and 2 icons in ResourceDictionary.

Answer 1

one more solution is to use a non-shared resource (x:Shared Microsoft docs)
<materialDesign:PackIcon x:Key="CashIcon" Kind="Cash" x:Shared="False"/>
x:Shared Attribute: When set to false, modifies WPF resource-retrieval behavior so that requests for the attributed resource create a new instance for each request instead of sharing the same instance for all requests.
A scenario for x:Shared="false" is if you define a FrameworkElement or FrameworkContentElement derived class as a resource and then you introduce the element resource into a content model. x:Shared="false" enables an element resource to be introduced multiple times in the same collection (such as a UIElementCollection). Without x:Shared="false" this is invalid because the collection enforces uniqueness of its contents. However, the x:Shared="false" behavior creates another identical instance of the resource instead of returning the same instance.

Answer 2

The PackIcon type is a Control. An element in the visual tree in WPF can only have a single parent. In other words, the pack icon is still a single instance added as child of the first button, then moved to the second, then to the third. You will in fact have to create multiple instances of the pack icon.
Instead of creating resources, you could use the PackIcon markup extension.
<StackPanel>
<Button Content="{materialDesign:PackIcon Cash}"/>
<Button Content="{materialDesign:PackIcon Cash}"/>
<Button Content="{materialDesign:PackIcon Cash}"/>
</StackPanel>
Depending on your actual scenario, you could alternatively create a DataTemplate, which will automatically create instances of the pack icons for each button.
<DataTemplate x:Key="CashPackIconTemplate">
<materialDesign:PackIcon Kind="Cash" />
</DataTemplate>
<StackPanel>
<Button ContentTemplate="{StaticResource CashPackIconTemplate}"/>
<Button ContentTemplate="{StaticResource CashPackIconTemplate}"/>
<Button ContentTemplate="{StaticResource CashPackIconTemplate}"/>
</StackPanel>