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WPF Issue Binding Menu Item

I have a problem with binding a menu command. I used MVVM pattern When I right click, a menu appears. But when I click on the menu item it doesn't work. You know why? Thanks to

Here's the 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>

Here is a small part of the ViewModel:

 #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
}

Mistake:

System.Windows.Data error: 40: BindingExpression path error: SavePNG property was not found in 'object' '' PlotModel '(HashCode = 15385318). BindingExpression: Path = SavePNG; DataItem = 'PlotModel' (HashCode = 15385318); the target item is "MenuItem" (Name = ''); target is "Command" (type "ICommand")

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3 answers


Your binding is trying to find SavePNG

in the Element , not your ViewModel.

Instead, give your view a name x: Name or Name and use the following binding instead:



{Binding DataContext.SavePNG, ElementName=theViewName}
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Assuming SaveCommand is on the same ViewModel that contains your collection.

ContextMenus are slightly different in wpf as they are not part of the control's visual tree. Thus, they cannot "see" any items by relative sources or by item names.



A bit of trickery to use the PlacementTarget property and get the datafile with it. Modify your ListView below to make it work. Notice the tag property in the ListView and DataContext properties in the ContextMenu.

<ListView Name="PlotLista"    SelectedIndex="{Binding SelectedValue}" ItemsSource="{Binding PlotModelList}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Tag="{Binding DataContext,ElementName=theViewName}">
            <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 DataContext="{Binding PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
                                <MenuItem Header="Export to PNG" Command="{Binding SavePNG}"/>
                            </ContextMenu>
                        </oxy:Plot.ContextMenu>
                    </oxy:Plot>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
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This was not written in visual studio, so please check the syntax:

  <ListView  Tag="{Binding Path=DataContext,ElementName=theViewName}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <oxy:Plot Tag="{Binding Path=Tag,RelativeSource={RelativeSource AncestorType=ListView}">
                    <oxy:Plot.ContextMenu>
                        <ContextMenu DataContext="{Binding PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
                            <MenuItem Command="{Binding SavePNG}"/>
                        </ContextMenu>
                    </oxy:Plot.ContextMenu>
                </oxy:Plot>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
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