WPF中override ResourceDictionary中的设置的方法

当资源文件里改变了控件的样式时，在使用的地方如果想改变资源文件里修改的内容，会造成无法达到预期目的的结果。

以DataGrid为例，我在资源文件里，改变了默认的DataGrid的样式，其中我设置了IsReadOnly为True。在使用时，这将导致DataGrid的列不能编辑；可实际情况要求编辑功能，我们就会想到针对列设置IsReadOnly为false。

如代码里的注释掉的内容所示，在简单地引用资源文件，而不做处理时，是无法达到预期的。

正确的做法是：

引入通过引入新的Style，在Style的Setter里设置，来override资源文件里的设置；这样再针对每个列单独设置IsReadOnly就会起作用。

其中的原理还没有太明白，仅仅记录下处理方法。

界面

<Window x:Class="learnwpf.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" WindowStartupLocation="CenterScreen">
    <Grid>
        <DataGrid x:Name="dg" AutoGenerateColumns="False"
                  CanUserAddRows="False" CanUserDeleteRows="False" CanUserReorderColumns="False"
                  CanUserResizeColumns="False" CanUserResizeRows="False" CanUserSortColumns="False">
            <!--以下这样的字典引用方式，将导致即使在DataGridTextColumn里设置IsReadOnly为false仍旧不能编辑-->
            <!--<DataGrid.Resources>
                <ResourceDictionary Source="newlook/DataGrid.xaml" />
            </DataGrid.Resources>-->
            <!--解决办法如下，注意x:key的使用-->
            <DataGrid.Resources>
                <ResourceDictionary>
                    <ResourceDictionary.MergedDictionaries>
                        <ResourceDictionary Source="newlook/DataGrid.xaml" />
                        <ResourceDictionary>
                            <Style TargetType="DataGrid">
                                <Setter Property="IsReadOnly" Value="False" />
                            </Style>
                        </ResourceDictionary>
                    </ResourceDictionary.MergedDictionaries>
                </ResourceDictionary>
            </DataGrid.Resources>
            <DataGrid.Columns>
                <DataGridTextColumn x:Name="text" Header="文本" Binding="{Binding Name,UpdateSourceTrigger=PropertyChanged,Mode=TwoWay}" IsReadOnly="True" />
                <DataGridTextColumn x:Name="combo" Header="选择" Binding="{Binding Class,UpdateSourceTrigger=PropertyChanged,Mode=TwoWay}" />
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

资源文件

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    
    <SolidColorBrush x:Key="GridHeaderForeground" Color="#333"/>
    <SolidColorBrush x:Key="GridHeaderLineBrush" Color="#FFCCCEDB"/>
    <SolidColorBrush x:Key="GridHeaderBackgroudBrush" Color="#FFE3E3E3"/>
    <SolidColorBrush x:Key="GridLineBrush" Color="#FFEFEFF2"/>
    <SolidColorBrush x:Key="GridDrakRow" Color="#FFF9F9F9"/>
    <SolidColorBrush x:Key="GridBorderBrush" Color="#FFCCCEDB"/>

    <Style x:Key="ColumnHeaderGripperStyle" TargetType="{x:Type Thumb}">
        <Setter Property="Width" Value="3" />
        <Setter Property="Background" Value="Transparent" />
        <Setter Property="Cursor" Value="SizeWE" />
        <Setter Property="Opacity" Value="0" />
    </Style>

    <Style TargetType="DataGrid">
        <Setter Property="Margin" Value="0"/>
        <Setter Property="CanUserResizeColumns" Value="True"/>
        <Setter Property="CanUserSortColumns" Value="False"/>
        <Setter Property="AutoGenerateColumns" Value="False"/>
        <Setter Property="CanUserResizeRows" Value="False"/>
        <Setter Property="SelectionMode" Value="Single"/>
        <Setter Property="RowHeaderWidth" Value="0"/>
        <Setter Property="CanUserAddRows" Value="False"/>
        <Setter Property="CanUserDeleteRows" Value="False"/>
        <Setter Property="IsReadOnly" Value="True"/>
        <Setter Property="Background" Value="AliceBlue" />
        <Setter Property="AlternationCount" Value="2" />
        <Setter Property="ClipToBounds" Value="True" />
        <Setter Property="BorderBrush" Value="{DynamicResource GridBorderBrush}" />
        <Setter Property="HorizontalGridLinesBrush" Value="{DynamicResource GridLineBrush}"/>
        <Setter Property="VerticalGridLinesBrush" Value="{DynamicResource GridLineBrush}"/>
    </Style>

    <Style TargetType="DataGridColumnHeader">
        <Setter Property="SnapsToDevicePixels" Value="True" />
        <Setter Property="Foreground" Value="{DynamicResource GridHeaderForeground}" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="DataGridColumnHeader">
                    <Border x:Name="BackgroundBorder" BorderThickness="1,0,1,1" 
                            Margin="-1,0,0,0"
                            Background="{DynamicResource GridHeaderBackgroudBrush}"
                            BorderBrush="{DynamicResource GridHeaderLineBrush}" Width="Auto">
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*" />
                            </Grid.ColumnDefinitions>
                            <ContentPresenter  Margin="0,0,0,0" VerticalAlignment="Center" HorizontalAlignment="Center"/>
                            <Thumb x:Name="PART_LeftHeaderGripper" HorizontalAlignment="Left" Style="{StaticResource ColumnHeaderGripperStyle}" />
                            <Thumb x:Name="PART_RightHeaderGripper" HorizontalAlignment="Right" Style="{StaticResource ColumnHeaderGripperStyle}" />
                        </Grid>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="Height" Value="25"/>
    </Style>

    <Style TargetType="{x:Type DataGridRow}">
        <Setter Property="Background" Value="Beige" />
        <Setter Property="SnapsToDevicePixels" Value="true" />
        <Setter Property="Height" Value="24" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type DataGridRow}">
                    <Border x:Name="DGR_Border" SnapsToDevicePixels="True">
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Normal" />
                                <VisualState x:Name="Unfocused_Selected">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="DGR_Border" Storyboard.TargetProperty="Background">
                                            <DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{DynamicResource CtrlSelectedUnFocusBG}" />
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Normal_AlternatingRow">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="DGR_Border" Storyboard.TargetProperty="Background">
                                            <DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{StaticResource GridDrakRow}" />
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="MouseOver">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="DGR_Border" Storyboard.TargetProperty="Background">
                                            <DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{DynamicResource CtrlMouseOverBG}" />
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Normal_Selected">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="DGR_Border" Storyboard.TargetProperty="Background">
                                            <DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{DynamicResource CtrlSelectedBG}" />
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <SelectiveScrollingGrid>
                            <SelectiveScrollingGrid.ColumnDefinitions>
                                <ColumnDefinition Width="Auto" />
                                <ColumnDefinition Width="*" />
                            </SelectiveScrollingGrid.ColumnDefinitions>
                            <SelectiveScrollingGrid.RowDefinitions>
                                <RowDefinition Height="*" />
                                <RowDefinition Height="Auto" />
                            </SelectiveScrollingGrid.RowDefinitions>
                            <DataGridCellsPresenter Grid.Column="1"
                                      ItemsPanel="{TemplateBinding ItemsPanel}"
                                      SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                            <DataGridDetailsPresenter Grid.Column="1"
                                        Grid.Row="1"
                                        Visibility="{TemplateBinding DetailsVisibility}"
                                        SelectiveScrollingGrid.SelectiveScrollingOrientation=
                  "{Binding AreRowDetailsFrozen, 
                  ConverterParameter={x:Static SelectiveScrollingOrientation.Vertical},
                  Converter={x:Static DataGrid.RowDetailsScrollingConverter}, 
                  RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
                            <DataGridRowHeader Grid.RowSpan="2"
                                 SelectiveScrollingGrid.SelectiveScrollingOrientation="Vertical"
                                 Visibility="{Binding HeadersVisibility, 
                  ConverterParameter={x:Static DataGridHeadersVisibility.Row}, 
                  Converter={x:Static DataGrid.HeadersVisibilityConverter}, 
                  RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" />
                        </SelectiveScrollingGrid>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsSelected" Value="True">
                            <Setter Property="Foreground" Value="Black" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</ResourceDictionary>

逻辑

using System.Collections.Generic;
using System.Windows;

namespace learnwpf
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            init();
        }

        private class TestData
        {
            public string Name { get; set; }
            public string Class { get; set; }
        }

        private void init()
        {
            List<TestData> data = new List<TestData>()
            {
                new TestData(){Name="first",Class="10"},
                new TestData(){Name="secon",Class="15"},
            };
            dg.ItemsSource = data;
        }
    }
}