WPF崩VS重新綁定

Question

我有如下因素代碼，我能夠重構：

<HierarchicalDataTemplate DataType = "{x:Type data:FieldMapping}" 
          ItemsSource = "{Binding Path=FieldMappingItems}"> 
    <Grid Name="MainGrid" > 
     <Grid.ToolTip > 
      <TextBlock Name="Tt" Text="{Binding Path=ToolTip}"/> 
     </Grid.ToolTip> 
     <Grid.ColumnDefinitions > 
      <ColumnDefinition Width="Auto"/> 
      <ColumnDefinition Width="Auto"/> 
      <ColumnDefinition Width="Auto"/> 
      <ColumnDefinition Width="*"/> 
     </Grid.ColumnDefinitions> 
     <TextBlock Name="Error" Margin="0,0,5,0" TextElement.FontWeight="Bold" TextElement.Foreground="Red" Visibility="Collapsed" Text="!"/> 
     <StackPanel Grid.Column="1" > 
      <Image Source="../../icons\column.png" Name="Image"/> 
      <Image Source="../../icons\Connect.png" Name="SourceImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\Service.png" Name="AttritubeImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\table.png" Name="SearchImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\surrogateKey.png" Name="TargetImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\Key16.png" Name="PrimayKeyImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\tempTable.png" Name="TempTableImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\Component16.png" Name="SPImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\DatabaseSelectCellSecure16.png" Name="RootImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\Console16.png" Name="ScriptImage" Visibility="Collapsed"/> 
      <Image Source="../../icons\CodeWindowSelect16.png" Name="ProgramImage" Visibility="Collapsed"/> 

     </StackPanel> 
     <TextBlock Name="tb" Margin="2,0,0,0" Grid.Column="2" Text="{Binding Path=FieldName}"/> 
     <TextBlock Name="tbSource" Margin="2,0,0,0" Visibility="Collapsed" Grid.Column="2" Text="{Binding Path=FullNodePath}"/> 
    </Grid> 
    <DataTemplate.Triggers>    
     <MultiDataTrigger > 
      <MultiDataTrigger.Conditions> 
       <Condition Binding="{Binding Path=Published}" Value="False"/> 
       <Condition Binding="{Binding Path=FieldMappingType}" Value="TempTable"/> 
      </MultiDataTrigger.Conditions> 
      <Setter TargetName="tb" Property="FontStyle" Value="Italic"/> 
     </MultiDataTrigger> 
     <DataTrigger Binding="{Binding Path=Active}" Value="False"> 
      <Setter TargetName="MainGrid" Property="Opacity" Value="0.5"/> 
     </DataTrigger> 
     <DataTrigger Binding="{Binding Path=IsPrimaryKey}" Value="True"> 
      <Setter TargetName="tb" Property="Margin" Value="4,0,0,0"/> 
      <Setter TargetName="Image" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="PrimayKeyImage" Property="Visibility" Value="Visible"/> 
      <Setter TargetName="SourceImage" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="TargetImage" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="RootImage" Property="Visibility" Value="Collapsed"/> 
     </DataTrigger> 
     <DataTrigger Binding="{Binding Path=FieldMappingType}" Value="Table"> 
      <Setter TargetName="tb" Property="Margin" Value="4,0,0,0"/> 
      <Setter TargetName="Image" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="SourceImage" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="PrimayKeyImage" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="TargetImage" Property="Visibility" Value="Visible"/> 
      <Setter TargetName="RootImage" Property="Visibility" Value="Collapsed"/> 
     </DataTrigger> 
     <DataTrigger Binding="{Binding Path=FieldMappingType}" Value="TempTable"> 
      <Setter TargetName="tb" Property="Margin" Value="4,0,0,0"/> 
      <Setter TargetName="Image" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="SourceImage" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="PrimayKeyImage" Property="Visibility" Value="Collapsed"/> 
      <Setter TargetName="TempTableImage" Property="Visibility" Value="Visible"/> 
      <Setter TargetName="RootImage" Property="Visibility" Value="Collapsed"/> 
      <!--<Setter TargetName="tb" Property="Margin" Value="15,0,0,0"/>--> 
     </DataTrigger> 
</HierarchicalDataTemplate> 

正如你可以看到有大量的圖片被倒塌後，根據不同的類型的對象，顯示期望的圖像。

我明白，這是一個爛攤子，我在下面的方式重構它：

<Grid Name="MainGrid"> 
       <Grid.ToolTip> 
        <TextBlock Name="Tt" Text="{Binding Path=ToolTip}" /> 
       </Grid.ToolTip> 

       <StackPanel Orientation="Horizontal"> 
        <TextBlock x:Name="Error" Margin="0,0,5,0" TextElement.FontWeight="Bold" TextElement.Foreground="Red" Visibility="{Binding Path=Warning, Converter={StaticResource BooleanToVisibility}}" Text="!"/> 
        <Image x:Name="Icon" Source="../../icons\column.png" /> 
        <TextBlock x:Name="tb" Margin="2,0,0,0" Text="{Binding Path=FieldName}" /> 
       </StackPanel> 

      </Grid> 
      <DataTemplate.Triggers> 

       <MultiDataTrigger> 
        <MultiDataTrigger.Conditions> 
         <Condition Binding="{Binding Path=Published}" Value="False" /> 
         <Condition Binding="{Binding Path=FieldMappingType}" Value="TempTable" /> 
        </MultiDataTrigger.Conditions> 
        <Setter TargetName="tb" Property="FontStyle" Value="Italic" /> 
       </MultiDataTrigger> 

       <DataTrigger Binding="{Binding Path=Active}" Value="False"> 
        <Setter TargetName="MainGrid" Property="Opacity" Value="0.5" /> 
       </DataTrigger> 

       <DataTrigger Binding="{Binding Path=IsPrimaryKey}" Value="True"> 
        <Setter TargetName="tb" Property="Margin" Value="4,0,0,0" /> 
        <Setter TargetName="Icon" Property="Source" Value="../../Icons/Key16.png" /> 
       </DataTrigger> 

       <DataTrigger Binding="{Binding Path=FieldMappingType}" Value="TempTable"> 
        <Setter TargetName="tb" Property="Margin" Value="4,0,0,0" /> 
        <Setter TargetName="Icon" Property="Source" Value="../../Icons/tempTable.png" /> 
       </DataTrigger> 

雖然我的重構是更容易消化，更succint，我在想，如果我通過改變獲得更好的性能綁定單個圖像而不是切換多個圖像的可視性。

Answer 1

它總是更高效地摺疊/顯示，而不是更改綁定。如果應用程序真的在速度上掙扎，這是一個簡單的勝利。

原因是，當綁定被改變時，幕後的WPF必須重新生成整個可視化樹。這很慢。如果WPF正在摺疊/顯示可視化樹的部分內容，那麼它會進行一些有效的優化，從而使此操作變得非常快速。諷刺的是，更改綁定直觀地吸引了程序員，而C＃通常更易於閱讀和更優雅。

更新

此規則僅適用於銷燬/創建巨大的可視樹。如果您的應用程序速度慢，那麼將其視爲優化，否則應避免將其編程爲更多工作​​。