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=""},
                 new TestData(){Name="secon",Class=""},
             };
             dg.ItemsSource = data;
         }
     }
 }