DictionaryKeyPropertyAttribute not working

[Kation]

Description

Class define with DictionaryKeyPropertyAttribute still show All objects added to an IDictionary must have a Key attribute or some other type of key associated with them. error while building project.

Reproduction Steps

Define a class with DictionaryKeyPropertyAttribute.

[DictionaryKeyProperty("TargetType")]
public class MyStyle
{
    public MyStyle()
    {

    }

    public Type TargetType { get; set; }
}

Use it in a xaml file.

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        xmlns:my="clr-namespace:WpfLibrary1;assembly=WpfLibrary1"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <ResourceDictionary>
            <my:MyStyle TargetType="{x:Type Butt
[WpfApp1.zip](https://github.com/dotnet/wpf/files/10802917/WpfApp1.zip)
on}"/>
        </ResourceDictionary>
    </Window.Resources>
    <Grid>
    </Grid>
</Window>

Expected behavior

Build successful

Actual behavior

Build failed

Regression?

No response

Known Workarounds

No response

Impact

No response

Configuration

No response

Other information

WpfApp1.zip

[ghost]

Here's a workaround

<!-- Set x:Key to have the same value as TargetType -->
<my:MyStyle x:Key="{x:Type Button}" TargetType="{x:Type Button}"/>

[Kation]

@tyl4r I means there have to fix this issure.
It's about xaml intellisense issure.
It can read successful by xaml reader.

[Nintynuts]

I'm also wondering why this isn't working. I've checked the source to work out how it obtains the key from DictionaryKeyPropertyAttribute and can't see why it would work for built-in types but not for custom ones (but it's quite hard to follow, so I might have missed it).

Here seems to be where it gets key from the property named by the attribute, (also here, but doesn't seem to use the value for anything) which throws SR.MissingKey which I can't seem to find, but I can't see anything which restricts the types it works with.

But there are two places where the MC3022 exception SR.ParserNoDictionaryKey is thrown.