How to use `SystemDropShadowChrome` in code?

[ahdung]

SystemDropShadowChrome in multiple assemblies, how to use one of them? I try to alias, not help:

[miloush]

You do not need to be adding any references.

<Window x:Class="DELwpfCORE.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:mwt="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero2"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <mwt:SystemDropShadowChrome CornerRadius="2" HorizontalAlignment="Left" VerticalAlignment="Top">
            <Ellipse Width="100" Height="100" Fill="Red" />
        </mwt:SystemDropShadowChrome>
    </Grid>
</Window>

or in code (just using Microsoft.Windows.Themes;)

But note that it might not do what you are hoping for, it always draws a rectangle:

[ahdung]

Thank you help, in code:

[gpaskaleva-msft]

@ahdung Since you've already declared the alias, I believe the only missing part is that you should reach the type through that root using the namespace-alias-qualifier operator as follows:

using Aero2Theme::Microsoft.Windows.Themes;

This means "the Microsoft.Windows.Themes namespace as seen only through the Aero2 reference." Because Aero2 is no longer part of global, this path has exactly one candidate for SystemDropShadowChrome.

Hope this helps!

[miloush]

See https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/extern-alias

[ahdung]

@gpaskaleva-msft @miloush Thank you guys for help, but you can't, trust me, this issue hits edge cases.
first, it is referenced by Framework, not manully, so can put this thing like docs said:

<Reference Include="grid.dll"> 
    <Aliases>GridV1</Aliases>
</Reference>

[ahdung]

@ahdung Since you've already declared the alias, I believe the only missing part is that you should reach the type through that root using the namespace-alias-qualifier operator as follows:

using Aero2Theme::Microsoft.Windows.Themes;
This means "the Microsoft.Windows.Themes namespace as seen only through the Aero2 reference." Because Aero2 is no longer part of global, this path has exactly one candidate for SystemDropShadowChrome.

Hope this helps!

can't reach that step, when declareing, it error

[gpaskaleva-msft]

@ahdung — the error you're hitting is expected: you can't add a new <Reference Include="…"> with <Aliases> for a theme assembly, because WPF already brings PresentationFramework.Aero2 in implicitly. A second manual <Reference> to the same assembly conflicts.

The fix is to attach the alias to the already-resolved reference instead of declaring a new one. I suggest you add this target to your .csproj :

<Target Name="AddThemeAlias" AfterTargets="ResolveReferences">
  <ItemGroup>
    <ReferencePath Condition="'%(FileName)' == 'PresentationFramework.Aero2'">
      <Aliases>Aero2Theme</Aliases>
    </ReferencePath>
  </ItemGroup>
</Target>

Then in your code-behind:

extern alias Aero2Theme;
using Aero2Theme::Microsoft.Windows.Themes;

// ...
var chrome = new SystemDropShadowChrome
{
    /* your content */
};

Running the alias assignment  AfterTargets="ResolveReferences" sets the Aliases metadata on the reference that's already in the graph, so extern alias has something to bind to — no manual  needed.

I built a small end-to-end sample this way (net10.0-windows) and it instantiates the type from code cleanly, resolving to PresentationFramework.Aero2. If it helps, I can share the full harness.