C# UWP项目如何正确添加WinUI控件

Question

I try to add Microsoft.UI.Xaml.Controls.TreeView in my C# UWP project. But when I debug my app LoadComponent(...) throws XamlParseException:

I follow all the steps described in Microsoft WinUI Docs . I don't need to create WinUI project.
My project properties:

My project links:

Application XAML:

<Application
    x:Class="SqlDBObjects.SqlDbApplication"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:controls="using:Microsoft.UI.Xaml.Controls"
    xmlns:local="using:SqlDBObjects">
    <Application.Resources>
        <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls"/>
    </Application.Resources>
</Application>

My main window content is custom control based on ContentControl. It's XAML fragment:

<ContentControl
    x:Class="SqlDBObjects.SqlDbContentControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:muxc="using:Microsoft.UI.Xaml.Controls"
    xmlns:mctk="using:Microsoft.Toolkit.Uwp.UI.Controls"
    xmlns:local="using:SqlDBObjects"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    Name="SQLDBContentControl"
    Background="LightGray"
    Loaded="OnLoaded">
    ...
    <muxc:TreeView
        Name="DBObjectTree"
        HorizontalAlignment="Stretch"
        VerticalAlignment="Stretch"
        Background="White"
        ItemsSource="{x:Bind Items, Mode=TwoWay}"
        ItemTemplate="{StaticResource DBOBJECT_TEMPLATE}"
        Expanding="OnTreeViewExpanding">
    </muxc:TreeView>
    ...
</ContentControl>

Answer 1

But when I debug my app LoadComponent(...) throws XamlParseException

I could reproduce your problem when missing add <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" /> . please follow Getting started with the Windows UI 2 Library document, and install Microsoft.UI.Xaml nuget version 2.7. then build your app. if the problem still exist, please clean your project or remove bin and obj folder.

Update

The problem is you custom app's entry point as SqlDbApplication , and this causes winui XamlControlsResources can't load correctly. please feel free post this problem in WinUI github issue box. Currently there is a workaround that is edit SqlDbApplication to App as the app's default entry point. (please don't forget update the entry-point within package manifest)