WPF 不对第一个元素应用样式 [英] WPF doesn't apply style to first element

问题描述

我有一个简单的 WPF 窗口，上面有 12 个按钮.我希望将相同的风格应用于所有这些.此代码产生相同的错误:

I have a simple WPF window that has 12 buttons on it. I want the same style to be applied to all of them. This code produces the same error:

<Window x:Class="TestApp.TestWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="TestWindow" Height="400" Width="500"
        WindowStyle="None" WindowState="Maximized">
    <Window.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="Resources/AllResources.xaml"/>
                <ResourceDictionary>
                    <Style TargetType="{x:Type Button}">
                        <Setter Property="FontSize" Value="100"/>
                    </Style>
                </ResourceDictionary>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Window.Resources>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Button Grid.Column="0" Content="1" Name="Button1"/>
        <Button Grid.Column="1" Content="2" Name="Button2"/>
    </Grid>
</Window>

第一个按钮没有应用样式，但第二个按钮有.我可以设置一个键并在每个按钮上使用它，但我更愿意让 WPF 为我处理.我刚刚在写这篇文章时发现，当我不包括外部 ResourceDictionary 时，它会按预期工作.随着我的应用程序扩展，因为我有多个窗口需要共享相同的资源，这将是未来的问题.修改后的代码如下:

The first button does not get the style applied to it, but the second one does. I could set a key and use that on every button, but I would prefer to let WPF handle that for me. I just found out while writing this that when I do not include the outside ResourceDictionary, it works as expected. This will be a problem in the future as my application expands as I have multiple windows that need to share the same resources. The modified code is as follows:

<Window x:Class="TestApp.TestWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="TestWindow" Height="400" Width="500"
        WindowStyle="None" WindowState="Maximized">
    <Window.Resources>
        <Style TargetType="{x:Type Button}">
            <Setter Property="FontSize" Value="100"/>
        </Style>
    </Window.Resources>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Button Grid.Column="0" Content="1" Name="Button1"/>
        <Button Grid.Column="1" Content="2" Name="Button2"/>
    </Grid>
</Window>

如果我(而不是删除合并的字典)添加一个 x:Key="key" 属性，然后将该样式显式分配给每个按钮，它也可以工作.

It also works if I (instead of removing the merged dictionaries) add an x:Key="key" attribute and then explicitly assign that style to each button.

这里有什么问题?为什么第一个跳过Button1"而第二个不跳过?

What is the issue here? Why does the first one skip "Button1" and the second not?

推荐答案

这个问题我已经见过几次了，这是一个非常奇怪的错误".当您将 Style 直接放在 内的 ResourceDictionary 中时，就会发生这种情况.Style 跳过第一项.此代码产生相同的结果，跳过第一个 ListBoxItem

I've seen this problem a couple of times before and it's a pretty weird "bug". It happends when you put a Style directly in a ResourceDictionary inside <ResourceDictionary.MergedDictionaries>. The Style is skipped for the first item. This code produces the same result, the Style is skipped for the first ListBoxItem

<Window.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary>
                <Style TargetType="{x:Type ListBoxItem}">
                    <Setter Property="Foreground" Value="Green"/>
                </Style>
            </ResourceDictionary>
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
</Window.Resources>
<ListBox>
    <ListBoxItem Content="Item 1"/>
    <ListBoxItem Content="Item 2"/>
    <ListBoxItem Content="Item 3"/>
</ListBox>

要使样式和 MergedDictionaries 都能工作，请改为这样做

To get both the styles and MergedDictionaries to work, do it like this instead

<Window.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="Resources/AllResources.xaml"/>
        </ResourceDictionary.MergedDictionaries>
        <Style TargetType="{x:Type Button}">
            <Setter Property="FontSize" Value="100"/>
        </Style>
    </ResourceDictionary>
</Window.Resources>
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition/>
        <ColumnDefinition/>
    </Grid.ColumnDefinitions>
    <Button Grid.Column="0" Content="1" Name="Button1"/>
    <Button Grid.Column="1" Content="2" Name="Button2"/>
</Grid>

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