c# - WPF MergedDictionaries - 值不能为 Null - 参数名称 : item

Question

我的 App.Resources MergedDictionary 有一个棘手的问题。每次从另一个程序集添加一个带有源和 XML 命名空间的新字典时，都会产生一个错误，我无法构建我的程序。

App.xaml 中出现错误，ResourceDictionary 带有下划线，消息 Value Cannot be Null。参数名称:item。这完全没有意义，因为我以前做过完全相同的事情。唯一的区别是这次，我引用了另一个程序集(c# 类库)的命名空间。这是 App.xaml 文件:

<Application x:Class="Quiz.Client.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:Quiz.Client"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="Resources/Styles.xaml" />
                <ResourceDictionary Source="Resources/Templates.xaml"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

下面是 Styles.xaml:

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:local="clr-namespace:Quiz.Client">

    <Style x:Key="StrongFont"
           TargetType="ContentControl">
        <Setter Property="FontSize"
                Value="20" />
        <Setter Property="FontWeight"
                Value="ExtraBold" />
        <Setter Property="Foreground"
                Value="DarkRed" />
    </Style>


</ResourceDictionary>

这是 Templates.xaml:

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:local="clr-namespace:Quiz.Client"
                    xmlns:domain="clr-namespace:Quiz.Core.Domain;assembly=Quiz.Core"
                    xmlns:common="clr-namespace:Quiz.Client.Common">

    <DataTemplate x:Key="ArithmeticQuestionTemplate"
                  DataType="domain:ArithmeticQuestion">

    </DataTemplate>

    <common:QuestionTemplateSelector x:Key="QuestionTemplateSelector"
                                     ArithmeticTemplate="{StaticResource ArithmeticQuestionTemplate}" />

</ResourceDictionary>

这到底是怎么回事？是否引入了软件破坏性更改或其他什么？我完全迷路了。

Answer 1

确认!!! Microsoft 跟踪了此错误。这意味着 WPF 在某些方面将尝试使用 Microsoft 报告过程自动向 Microsoft 报告。报告期间VS启动卡住。请等待错误报告完成。

该错误在 lattes VS 2019 中仍然存在。

重启后一切正常。确认!!!

Thanks for the answer. I believe it is a Visual Studio bug caused by something unknown. Maybe one of my plugins, who knows. The only thing that fixes the issue is restarting visual studio and building the project. The problem seems to begin when adding a new namespace from another assembly. The project then can't build until visual studio is restarted. Very weird, never seen anything like it before. – user3096803