What's the correct syntax for third-party control design-time property assign?

[GF-Huang]

<UserControl ...
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             xmlns:hc="xxx">
  <hc:TagContainer>
    <d:hc:TagContainer.Items>  // syntax errors
      <hc:Tag />
      <hc:Tag />
      <hc:Tag />
    </d:hc:TagContainer.Items>
  </hc:TagContainer>
</UserControl>

Where hc:TagContainer:

[lindexi]

It works well in design time.

You must use the HandyControl design version, see

<Window x:Class="CarkugeajeKejoheele.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:CarkugeajeKejoheele"
        xmlns:hc="https://handyorg.github.io/handycontrol"
        xmlns:hcDesignTimeControls="https://handyorg.github.io/handycontrol/design"
        mc:Ignorable="d hcDesignTimeControls"
        Title="MainWindow" Height="450" Width="800">
  <Grid>
    <hc:TagContainer>
      <hcDesignTimeControls:TagContainer.Items>
        <hc:Tag>
          <hc:Tag.Content>
            <TextBlock>123</TextBlock>
          </hc:Tag.Content>
        </hc:Tag>
        <hc:Tag Content="2" />
        <hc:Tag Content="3" />
      </hcDesignTimeControls:TagContainer.Items>
    </hc:TagContainer>
  </Grid>
</Window>

[GF-Huang]

How can you know this one: xmlns:hcDesignTimeControls="https://handyorg.github.io/handycontrol/design"?

Where is the docs?

[lindexi]

@GF-Huang See https://github.com/HandyOrg/HandyControl/

https://blog.lindexi.com/post/WPF-%E5%BC%95%E7%94%A8%E7%AC%AC%E4%B8%89%E6%96%B9%E5%BA%93%E7%9A%84%E6%8E%A7%E4%BB%B6%E5%9C%A8%E8%AE%BE%E8%AE%A1%E5%99%A8%E5%8A%A0%E4%B8%8A%E8%AE%BE%E8%AE%A1%E6%97%B6%E6%95%B0%E6%8D%AE%E5%92%8C%E5%B1%9E%E6%80%A7.html