[WPF]解决模板中ContextMenu绑定CommandParameter的问题

直接上代码，首先是一个ContextMenu的模板：

<ContextMenu x:Key="Menu" BorderThickness="0.3" FontSize="13" DataContext="{Binding PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
        <MenuItem Header="复制" Command="{Binding Source={x:Static vm:ViewModelLocator.Instance},Path=MainWindowVM.CopyImageCommand}"
                  CommandParameter="{Binding PlacementTarget.DataContext, RelativeSource={RelativeSource AncestorType=ContextMenu}}" CommandTarget="{Binding PlacementTarget, RelativeSource={RelativeSource Self}}" />
        <MenuItem Header="另存为..." Command="{Binding Source={x:Static vm:ViewModelLocator.Instance},Path=MainWindowVM.SaveImageCommand}"
                  CommandParameter="{Binding PlacementTarget.DataContext, RelativeSource={RelativeSource AncestorType=ContextMenu}}" CommandTarget="{Binding PlacementTarget, RelativeSource={RelativeSource Self}}" />
    ContextMenu>

然后是DataTemplate的内容：

<DataTemplate x:Key="CustomerImageDataTemplate">
            <Button Command="{Binding DataContext.ShowImageCommand, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}" Cursor="Hand"
                    CommandParameter="{Binding Path=DataContext, RelativeSource={RelativeSource Mode=FindAncestor, AncestorLevel=1,AncestorType=StackPanel}}" Padding="3">
                <Button.Template>
                    <ControlTemplate TargetType="Button">
                        <Grid>
                            <Border  Name="imgBorder"  BorderBrush="{StaticResource ListBorder}" CornerRadius="3" BorderThickness="0"
                                Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}" Margin="0">
                            Border>
                            <Image x:Name="ImageMsg" Source="{Binding TextContent}" Stretch="Uniform" Width="120" Height="80"
                                   ContextMenu="{StaticResource Menu}" Tag="{Binding}">
                                <Image.OpacityMask>
                                    <VisualBrush Visual="{Binding ElementName=imgBorder, Mode=OneTime}" />
                                Image.OpacityMask>
                            Image>
                        Grid>
                    ControlTemplate>
                Button.Template>
            Button>
    DataTemplate>

上面的Button还展示了将图片四角设置为圆角的方法。

补充后来修改过的ContextMenu和模板：

<ContextMenu x:Key="Menu" BorderThickness="0.3" FontSize="13" DataContext="{Binding PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
    <MenuItem x:Name="MntCopy"  Header="复制" Command="{Binding Source={x:Static vm:ViewModelLocator.MainWindowVM},Path=CopyImageCommand}" FlowDirection="LeftToRight"
              CommandParameter="{Binding PlacementTarget.DataContext, RelativeSource={RelativeSource AncestorType=ContextMenu}}" CommandTarget="{Binding PlacementTarget, RelativeSource={RelativeSource Self}}" />
    <MenuItem x:Name="MntSaveAs" Header="另存为..." Command="{Binding Source={x:Static vm:ViewModelLocator.MainWindowVM},Path=SaveImageCommand}" FlowDirection="LeftToRight"
              CommandParameter="{Binding PlacementTarget.DataContext, RelativeSource={RelativeSource AncestorType=ContextMenu}}" CommandTarget="{Binding PlacementTarget, RelativeSource={RelativeSource Self}}" />
    <MenuItem Header="撤回" Command="{Binding Source={x:Static vm:ViewModelLocator.MainWindowVM},Path=WithdrawCommand}" FlowDirection="LeftToRight"
              CommandTarget="{Binding PlacementTarget, RelativeSource={RelativeSource Self}}"
              CommandParameter="{Binding PlacementTarget.DataContext.MsgID, RelativeSource={RelativeSource AncestorType=ContextMenu}}"/>
ContextMenu>

<Button Command="{Binding Source={x:Static vm:ViewModelLocator.MainWindowVM}, Path=ShowImageCommand}" Cursor="Hand" Margin="5,0,0,0"
        CommandParameter="{Binding Path=DataContext, RelativeSource={RelativeSource Mode=FindAncestor, AncestorLevel=1,AncestorType=StackPanel}}" Padding="3">
    <Button.Template>
        <ControlTemplate TargetType="Button">
            <Grid>
                <Border Name="imgBorder" BorderBrush="{StaticResource ListBorder}" CornerRadius="0" BorderThickness="0"
                            Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"
                            ContextMenu="{StaticResource Menu}" Tag="{Binding}">
                Border>
                <Image x:Name="ImageMsg" Source="{Binding TextContent}" Stretch="Uniform" MinWidth="20" MinHeight="50" MaxWidth="150" MaxHeight="150"
                           ContextMenu="{StaticResource Menu}" Tag="{Binding}">
                    <Image.OpacityMask>
                        <VisualBrush Visual="{Binding ElementName=imgBorder, Mode=OneTime}" />
                    Image.OpacityMask>
                Image>
            Grid>
        ControlTemplate>
    Button.Template>
    <Button.InputBindings>
        <MouseBinding MouseAction="RightClick" Command="{Binding Source={x:Static vm:ViewModelLocator.MainWindowVM}, Path=MsgContextMenuCommand}"
                      CommandParameter="{Binding Path=DataContext, RelativeSource={RelativeSource Mode=FindAncestor, AncestorLevel=1,AncestorType=StackPanel}}"/>
    Button.InputBindings>
Button>