c# - 菜单项绑定(bind) WPF 问题

Question

我对菜单项命令绑定(bind)有疑问。我使用了 MVVM 模式当我使用右键单击时，会出现菜单。但是当我点击菜单项时不起作用。你知道为什么吗？谢谢

这是 XAML:

    <UserControl x:Class="PlotView.ViewModel.PlotViewControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:oxy="http://oxyplot.org/wpf"
             mc:Ignorable="d" 
             xmlns:diagnostics="clr-namespace:System.Diagnostics;assembly=WindowsBase"
             d:DesignHeight="400" d:DesignWidth="600"
             x:Name="theViewName">

    <UserControl.Resources>
    </UserControl.Resources>

    <GroupBox  Name="GB" Header="Graphs"  HorizontalAlignment="Stretch" VerticalAlignment="Stretch"  BorderThickness="0">
        <ListView Name="PlotLista"    SelectedIndex="{Binding SelectedValue}" ItemsSource="{Binding PlotModelList}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" >
            <ListView.ItemTemplate>
                <DataTemplate>
                    <oxy:Plot  MinHeight="260" Height="Auto"   IsRendering="True" FontStyle="Normal" FontFamily="Arial" FontSize="8"  VerticalContentAlignment="Top"  HorizontalContentAlignment="Left" Width="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UserControl}}, Path=ActualWidth}"  Model="{Binding }">
                        <oxy:Plot.ContextMenu>
                            <ContextMenu>
                                <MenuItem Header="Export to PNG" Command="{Binding DataContext.SavePNG, ElementName=theViewName}"/>
                            </ContextMenu>
                        </oxy:Plot.ContextMenu>
                    </oxy:Plot>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </GroupBox>
</UserControl>

这里是 ViewModel 的一小部分:

 #region Fields
        private readonly DelegateCommand _menuClick=new DelegateCommand(this.MenuItemClick);
  #endregion

  #region Command
 public ICommand SavePNG
 {
   get { return this._menuClick; }
 }
  #endregion

 private void MenuItemClick()
{
   // some code here
}

错误:

System.Windows.Data Error: 40 : BindingExpression path error: 'SavePNG' property not found on 'object' ''PlotModel' (HashCode=15385318)'. BindingExpression:Path=SavePNG; DataItem='PlotModel' (HashCode=15385318); target element is 'MenuItem' (Name=''); target property is 'Command' (type 'ICommand')

Answer 1

您的绑定(bind)试图在您的 Item 上找到 SavePNG，而不是在您的 ViewModel 上。

相反，为您的 View 提供一个 x:Name 或名称，并改用以下绑定(bind):

{Binding DataContext.SavePNG, ElementName=theViewName}