迁移到 .NET 8 后，自定义控件在 XAML 中不可见

Question

我最近将我的项目从 .NET 4.8.1 迁移到 .NET 8。在我的项目中，我在

Themes.Generic.xaml

ResourceDictionary 中实现了一个自定义控件，并且包含 DependencyProperties 的 C# 实现位于

MyProject.CustomControls

命名空间中。

迁移后，我的自定义控件在 XAML 中不可见。它们显示为宽度为零的空矩形。如果我手动扩展宽度，我会得到空矩形。

这是我的

Generic.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"
    xmlns:local="clr-namespace:FloatingLabelComboBox">

    <Style TargetType="{x:Type local:CustomControls.FloatingLabelComboBox}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type local:CustomControls.FloatingLabelComboBox}">
                    <StackPanel FlowDirection="LeftToRight">
                        <Label Content="{TemplateBinding LabelText}"
                               Foreground="{TemplateBinding LabelForeground}"
                               FontSize="{TemplateBinding LabelFontSize}"
                               VerticalAlignment="Stretch"
                               Margin="-5 0 0 0" 
                        />

                        <ComboBox x:Name="comboBox"
                                  ItemsSource="{TemplateBinding ItemsSource}"
                                  SelectedItem="{TemplateBinding SelectedItem}"
                                  SelectedValuePath="{TemplateBinding SelectedValuePath}"
                                  SelectedValue="{TemplateBinding SelectedValue}"
                                  DisplayMemberPath="{TemplateBinding DisplayMemberPath}"
                                  HorizontalAlignment="Stretch"
                                  VerticalAlignment="Center"
                                  Width="Auto"
                                  Height="Auto"
                                  materialdesign:HintAssist.IsFloating="False"
                                  materialdesign:ColorZoneAssist.Mode="Dark"
                                  materialdesign:HintAssist.HintOpacity="0.10"
                                  materialdesign:HintAssist.FontFamily="Century Gothic"
                                  Foreground="{TemplateBinding Foreground}">

                        </ComboBox>
                    </StackPanel>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

这是包含 DependencyProperties 的 C# 实现：

using System.Collections;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;

namespace FloatingLabelComboBox.CustomControls
{
    public class FloatingLabelComboBox : Control
    {
        static FloatingLabelComboBox()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(FloatingLabelComboBox), new FrameworkPropertyMetadata(typeof(FloatingLabelComboBox)));
        }

        public static readonly DependencyProperty LabelTextProperty =
            DependencyProperty.Register("LabelText", typeof(string), typeof(FloatingLabelComboBox), new PropertyMetadata("LabelText"));

        public string LabelText
        {
            get { return (string)GetValue(LabelTextProperty); }
            set { SetValue(LabelTextProperty, value); }
        }

        public static readonly DependencyProperty LabelForegroundProperty =
            DependencyProperty.Register("LabelForeground", typeof(Brush), typeof(FloatingLabelComboBox), new PropertyMetadata(new SolidColorBrush((Color)ColorConverter.ConvertFromString("#FFD6931B"))));

        public Brush LabelForeground
        {
            get { return (Brush)GetValue(LabelForegroundProperty); }
            set { SetValue(LabelForegroundProperty, value); }
        }

        public static readonly DependencyProperty LabelFontSizeProperty =
            DependencyProperty.Register("LabelFontSize", typeof(double), typeof(FloatingLabelComboBox), new PropertyMetadata(10.0));

        public double LabelFontSize
        {
            get { return (double)GetValue(LabelFontSizeProperty); }
            set { SetValue(LabelFontSizeProperty, value); }
        }

        public static readonly DependencyProperty ItemsSourceProperty =
            DependencyProperty.Register("ItemsSource", typeof(IEnumerable), typeof(FloatingLabelComboBox), new PropertyMetadata(null));

        public IEnumerable ItemsSource
        {
            get { return (IEnumerable)GetValue(ItemsSourceProperty); }
            set { SetValue(ItemsSourceProperty, value); }
        }

        public static readonly DependencyProperty SelectedItemProperty =
            DependencyProperty.Register("SelectedItem", typeof(object), typeof(FloatingLabelComboBox), new PropertyMetadata(null));

        public object SelectedItem
        {
            get { return GetValue(SelectedItemProperty); }
            set { SetValue(SelectedItemProperty, value); }
        }

        public static readonly DependencyProperty SelectedValuePathProperty =
            DependencyProperty.Register("SelectedValuePath", typeof(string), typeof(FloatingLabelComboBox), new PropertyMetadata(null));

        public string SelectedValuePath
        {
            get { return (string)GetValue(SelectedValuePathProperty); }
            set { SetValue(SelectedValuePathProperty, value); }
        }

        public static readonly DependencyProperty SelectedValueProperty =
            DependencyProperty.Register("SelectedValue", typeof(object), typeof(FloatingLabelComboBox), new PropertyMetadata(null));

        public object SelectedValue
        {
            get { return GetValue(SelectedValueProperty); }
            set { SetValue(SelectedValueProperty, value); }
        }

        public static readonly DependencyProperty DisplayMemberPathProperty =
            DependencyProperty.Register("DisplayMemberPath", typeof(string), typeof(FloatingLabelComboBox), new PropertyMetadata(null));

        public string DisplayMemberPath
        {
            get { return (string)GetValue(DisplayMemberPathProperty); }
            set { SetValue(DisplayMemberPathProperty, value); }
        }
    }
}

我已检查以下内容：

• 在XAML中正确声明了自定义控件的命名空间 文件。
• DefaultStyleKeyProperty 在静态构造函数中被重写 自定义控件类的。
• AssemblyInfo.cs 文件包含必要的条目。
• 解决方案已重建。

XAML 文件的构建操作是“Page”，对于 C# 文件来说，构建操作是“C# 编译器”。在 .NET 4.8.1 中，构建操作是“编译”。

这是完整项目的 github 存储库，任何帮助将不胜感激。

Answer 1

您应该将

ThemeInfo

属性添加到您的 .NET 8 程序集中：

using System.Windows;

[assembly: ThemeInfo(
    ResourceDictionaryLocation.None,
    ResourceDictionaryLocation.SourceAssembly
)]

Answer 2

哦！，我在 Generic.xaml 中发现了问题

 x:Key="MyCustomControl"

。删除后一切正常。