Question

您好，我是初学者程序员，也是WPF的新手，并且有一个简单的问题，但我花了很长时间搜索它无法理解，所以我希望你们能帮助我。我想要的是禁用我的Datagrid中的上下文菜单中的菜单项。例如：如果在Datagrid中选择了多个行，则禁用上下文菜单项＆＃34;属性＆＃34;

<DataGrid.Resources>
    <ContextMenu  x:Key="DataRowContextMenu">
            <MenuItem x:Name="RowContMenuProp"  Header="Properties">
                <MenuItem.Icon>
                    <Image Source="Resources/proporties.ico" Height="16" Width="16" />
                </MenuItem.Icon>
            </MenuItem>
            <Separator Margin="0"  />
            <MenuItem Header="Copy" Command="Copy" >
                <MenuItem.Icon>
                    <Image Source="Resources/copy.ico" Height="16" Width="16" />
                </MenuItem.Icon>
            </MenuItem>
            <MenuItem Header="Remove from list" Click="MenuItem_Click_1" >
                <MenuItem.Icon>
                    <Image Source="Resources/cut.png" Height="16" Width="16" />
                </MenuItem.Icon>
            </MenuItem>
            <MenuItem Header="Remove from project" Click="MenuItem_Click_2" >
                <MenuItem.Icon>
                    <Image Source="Resources/remove.ico" Height="16" Width="16" />
                </MenuItem.Icon>
            </MenuItem>
    </ContextMenu>
</DataGrid.Resources>

<DataGrid.RowStyle >
    <Style TargetType="{x:Type DataGridRow}">
        <Setter Property="ContextMenu" Value="{StaticResource DataRowContextMenu}" />
        <Setter Property="BorderThickness" Value="0"/>
    </Style>
</DataGrid.RowStyle>

- 禁用上下文菜单项

Private Sub datagrid1_MouseUp(sender As Object, e As MouseButtonEventArgs)
        If datagrid1.SelectedItems.Count > 1 Then

Answer 1

这是一种解决方法。它有点脏，但有效。

首先创建一个IValueConverter来表示1表示启用（true），而Value Converter可能看起来像这样

public class OneReturnsTrueConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return (int)value == 1;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

然后在DataGridRow中保存对DataGrid的引用

<DataGrid.RowStyle >
    <Style TargetType="{x:Type DataGridRow}">
        <Setter Property="Tag" Value="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGrid}}}" />
        <Setter Property="ContextMenu" Value="{StaticResource DataRowContextMenu}" />
        <Setter Property="BorderThickness" Value="0"/>
    </Style>
</DataGrid.RowStyle>

最后将网格的SelectedItems计数绑定到IsEnabled属性

<DataGrid.Resources>
    <myConverters:OneReturnsTrueConverter x:Key="OneReturnsTrueConverter"/>
    <ContextMenu  x:Key="DataRowContextMenu">
        <MenuItem x:Name="RowContMenuProp"  Header="Properties"
                  DataContext="{Binding Parent.PlacementTarget.Tag , RelativeSource={RelativeSource Self}}"
                  IsEnabled="{Binding Path=SelectedItems.Count, Converter={StaticResource OneReturnsTrueConverter}}" />
    </ContextMenu>
</DataGrid.Resources>

Answer 2

看看WPF Command pattern implementation。命令可以通过实现CanExecute方法指示是否可以执行操作。按钮可以订阅CanExecuteChanged事件，如果CanExecute返回false，则被禁用;如果CanExecute返回true，则被启用

您可以轻松地根据需要调整MSDN页面中的代码。

<MenuItem x:Name="RowContMenuProp" Header="Properties" Command="local:ApplicationsCmd.ShowProperties" CanExecute="ShowPropertiesCanExecute" Executed="ShowPropertiesExecuted" >

然后在代码中：

Private Sub ShowPropertiesExecuted(ByVal sender As Object, ByVal e As ExecutedRoutedEventArgs) ... End Sub Private Sub ShowPropertiesCanExecute(ByVal sender As Object, ByVal e As CanExecuteRoutedEventArgs) e.CanExecute = ...set to True when your condition is met End Sub

WPF数据网格行上下文菜单 - 禁用菜单项

2 个答案: