c# - WPF 窗口按钮(关闭、最大、最小、恢复)绑定(bind)到系统命令失败

Question

编辑

我已经更正了输出窗口中引用的绑定(bind)问题:

System.Windows.Data Information: 41 : BindingExpression path error: 'Source{x:Static SystemCommands' property not found for 'object' because data item is null. This could happen because the data provider has not produced any data yet. BindingExpression:Path=Source{x:Static SystemCommands.CloseWindowCommand}; DataItem=null; target element is 'Button' (Name='Close'); target property is 'Command' (type 'ICommand')

我错过了 Source 和 {

之间的 =

在输出窗口的每一行中都提到了这一点，如下所述，但是解决这个问题并没有解决按钮仍然没有任何作用的问题。

输出窗口现在充满了以下内容，所有不是我的窗口按钮的引用控件:

System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=Source{x:Static SystemCommands.CloseWindowCommand}; DataItem=null; target element is 'Button' (Name='Close'); target property is 'Command' (type 'ICommand')

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原始问题

基于对 SO 的一些回答，我构建了以下按钮来关闭、最大化、恢复和最小化我的窗口:

<!--Close Button-->
<Button x:Name="Close" Style="{StaticResource TitleButton}"
        Command="{Binding Source={x:Static SystemCommands.CloseWindowCommand}}"
        CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">
    <Grid Width="30" Height="25">
        <Path x:Name="Cross" Data="M0,0 L1,1 M0,1 L1,0" Stretch="Fill" Width="8" Height="8"
              Stroke="{Binding Foreground, RelativeSource={RelativeSource AncestorType={x:Type Button}, Mode=FindAncestor}}" StrokeThickness="2" />
    </Grid>
</Button>

<!--Maximize Button-->
<Button x:Name="Maximize" Style="{StaticResource TitleButton}"
        Command="{Binding Source={x:Static SystemCommands.MaximizeWindowCommand}}"
        CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" >
    <Grid Width="30" Height="25">
        <Path Data="M0,1 L9,1 L9,8 L0,8 Z" Width="9" Height="8" VerticalAlignment="Center" HorizontalAlignment="Center"
              Stroke="{Binding Foreground, RelativeSource={RelativeSource AncestorType={x:Type Button}, Mode=FindAncestor}}" StrokeThickness="2"  />
    </Grid>
</Button>

<!--Restore Button-->
<Button x:Name="Restore" Visibility="Collapsed" Style="{StaticResource TitleButton}"
        Command="{Binding Source={x:Static SystemCommands.RestoreWindowCommand}}"
        CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">
    <Grid Width="30" Height="25" UseLayoutRounding="True" RenderTransform="1,0,0,1,.5,.5">
        <Path Data="M2,0 L8,0 L8,6 M0,3 L6,3 M0,2 L6,2 L6,8 L0,8 Z" Width="8" Height="8" VerticalAlignment="Center" HorizontalAlignment="Center"
              Stroke="{Binding Foreground, RelativeSource={RelativeSource AncestorType={x:Type Button}, Mode=FindAncestor}}" StrokeThickness="1"  />
    </Grid>
</Button>

<!--Minimize Button-->
<Button x:Name="Minimize" Style="{StaticResource TitleButton}"
        Command="{Binding Source={x:Static SystemCommands.MinimizeWindowCommand}}"
        CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">
    <Grid Width="30" Height="25">
        <Path Data="M9,0 L8,1 8,1 8,1 0,1 0,1 z" Width="9" Height="9" VerticalAlignment="Bottom" HorizontalAlignment="Center"
              Stroke="{Binding Foreground, RelativeSource={RelativeSource AncestorType={x:Type Button}, Mode=FindAncestor}}" StrokeThickness="2" />
    </Grid>
</Button>

我已经与其他一些知识渊博的开发人员一起检查了绑定(bind)，他们说绑定(bind)看起来不错，但也许我需要一个 namespace 。在他们能够澄清之前，他们必须离开。

Visual Studio 中的输出窗口显示以下错误(自相矛盾的是，所有这些似乎都与关闭窗口按钮相关，这是唯一具有 TitleButton 样式的按钮正在努力。

似乎这里存在某种数据绑定(bind)问题，这很奇怪，因为我显然不需要将它们绑定(bind)到数据...我确实找到了一些关于 SO 的答案，但似乎都在处理其他事情:

• How to hide wpf datagrid columns depending on a property
• ElementName Binding is failing

System.Windows.Data Information: 41 : BindingExpression path error: 'Source{x:Static SystemCommands' property not found for 'object' because data item is null. This could happen because the data provider has not produced any data yet. BindingExpression:Path=Source{x:Static SystemCommands.CloseWindowCommand}; DataItem=null; target element is 'Button' (Name='Close'); target property is 'Command' (type 'ICommand')

System.Windows.Data Information: 20 : BindingExpression cannot retrieve value due to missing information. BindingExpression:Path=Source{x:Static SystemCommands.CloseWindowCommand}; DataItem=null; target element is 'Button' (Name='Close'); target property is 'Command' (type 'ICommand')

System.Windows.Data Information: 21 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=Source{x:Static SystemCommands.CloseWindowCommand}; DataItem=null; target element is 'Button' (Name='Close'); target property is 'Command' (type 'ICommand')

System.Windows.Data Information: 20 : BindingExpression cannot retrieve value due to missing information. BindingExpression:Path=Source{x:Static SystemCommands.CloseWindowCommand}; DataItem=null; target element is 'Button' (Name='Close'); target property is 'Command' (type 'ICommand')

System.Windows.Data Information: 21 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=Source{x:Static SystemCommands.CloseWindowCommand}; DataItem=null; target element is 'Button' (Name='Close'); target property is 'Command' (type 'ICommand')

System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=Source{x:Static SystemCommands.CloseWindowCommand}; DataItem=null; target element is 'Button' (Name='Close'); target property is 'Command' (type 'ICommand')

Answer 1

当使用静态 SystemCommands 类中的静态路由命令时，您不需要使用绑定(bind)，而是可以将您的 xaml 简化为以下内容。

Command="{x:Static SystemCommands.MinimizeWindowCommand}"