带有ResourceDictionary（WPF）的App.xaml中的“值不能为空”错误

Question

Using .NET Framework 4.6.1 and I'm using a UI kit that I've installed via NuGet and they are referenced correctly in the project.

App.xaml

<Application x:Class="ExampleApp.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:adonisUi="clr-namespace:AdonisUI;assembly=AdonisUI"
             xmlns:local="clr-namespace:ExampleApp"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="{x:Static adonisUi:ResourceLocator.DarkColorScheme}" />
                <ResourceDictionary Source="{x:Static adonisUi:ResourceLocator.ClassicTheme}" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

MainWindow.xaml

<Window x:Class="ExampleApp.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:ExampleApp"
        mc:Ignorable="d"
        Title="MainWindow"
        Height="450"
        Width="800">
    <Window.Style>
        <Style TargetType="Window"
               BasedOn="{StaticResource {x:Type Window}}" />
    </Window.Style>
    <Grid>
        <StackPanel Margin="10">
            <Button Content="Click Me"
                    HorizontalAlignment="Center" />
        </StackPanel>
    </Grid>
</Window>

Issues:

<ResourceDictionary Source="{x:Static adonisUi:ResourceLocator.DarkColorScheme}" />
<ResourceDictionary Source="{x:Static adonisUi:ResourceLocator.ClassicTheme}" />

Both lines in App.xaml are getting the following error:

Value cannot be null. Parameter name: item.

I have tried multiple fresh projects, building and rebuilding and I keep getting this error. I am able to build the project and I can see the styles from the UI kit correctly applied on MainWindow even though the error is still there.

However the styles don't appear on the designer window, I'm not sure if it's related to the error I'm getting or not.

Any ideas what could cause this?

Answer 1

I just tried it and it does the same thing to me... using Visual Studio Enterprise 2017 15.9.7

If you look at AdonisUI.ResourceLocator in a decompiler (I used Telerik's JustDecompile), you'll see the definitions:

public static Uri ClassicTheme
{
    get
    {
        return new Uri("pack://application:,,,/AdonisUI.ClassicTheme;component/Resources.xaml", UriKind.Absolute);
    }
}

public static Uri DarkColorScheme
{
    get
    {
        return new Uri("pack://application:,,,/AdonisUI;component/ColorSchemes/Dark.xaml", UriKind.Absolute);
    }
}

public static Uri LightColorScheme
{
    get
    {
        return new Uri("pack://application:,,,/AdonisUI;component/ColorSchemes/Light.xaml", UriKind.Absolute);
    }
}

If you change your App.xaml to reference using these values then it works.

<ResourceDictionary Source="pack://application:,,,/AdonisUI.ClassicTheme;component/Resources.xaml" />
<ResourceDictionary Source="pack://application:,,,/AdonisUI;component/ColorSchemes/Dark.xaml" />