WPF-将参数传递给ItemsControl中的relaycommand

Question

I've got an ItemsControl for basically an array of comboboxes, textboxes and buttons:

The XAML for that bottom section is all within the ItemsControl: (Having a problem with the button, the last element)

    <ItemsControl Grid.Row="2"
                  ItemsSource="{Binding CommandLinesOc}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Vertical" />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>
                    <Label Content="Send Command:"
                           HorizontalAlignment="Right"
                           Grid.Row="1" />
                    <ComboBox Grid.Column="1"
                              Grid.Row="1"
                              ItemsSource="{Binding ChromaCommandsCvs.View}"
                              SelectedItem="{Binding SelectedChromaCommand, UpdateSourceTrigger=PropertyChanged}" />
                    <Label Grid.Column="2"
                           Grid.Row="1"
                           Content="Parameter:"
                           HorizontalAlignment="Right" />
                    <TextBox Grid.Column="3"
                             Grid.Row="1"
                             Text="{Binding Parameter, UpdateSourceTrigger=PropertyChanged}" />
                    <Button Grid.Column="4"
                            DataContext="ChromaGUI.MainWindow"
                            Grid.Row="1"
                            Content="Send"
                            HorizontalAlignment="Center"
                            FontSize="15"
                            Command="{Binding RelativeSource=
                                {RelativeSource Mode=FindAncestor, 
                                AncestorType={x:Type Window}}, 
                                Path=DataContext.SendMessageCommand}"
                            CommandParameter="{Binding FullCommandString}"/>
                </Grid>
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>

As you can see, I've got the button element bound to a relay command. I had to use the main window relative source since the ItemsControl is setting the data context to an item in CommandLinesOc.

That all works fine - the problem is that CommandParameter seems to be inheriting the same relative source context, as I can't get FullCommandString (or any other property of one of the items in the observable collection, like Parameter or SelectedChromaCommand) to resolve to anything. So my question is, can I (and how do I) set the data context for the CommandParameter to be what the ItemsControl is giving me, while keeping the context for the Command the parent window?

Answer 1

Currently, you have the button DataContext set to a string "ChromaGUI.MainWindow" :

<Button DataContext="ChromaGUI.MainWindow"
        .......
        Command="{Binding RelativeSource=
            {RelativeSource Mode=FindAncestor, 
            AncestorType={x:Type Window}}, 
            Path=DataContext.SendMessageCommand}"
        CommandParameter="{Binding FullCommandString}"/>

String doesn't have property FullCommandString , so your command parameter binding will fail. Simply remove DataContext setting in the button to make it use default DataContext which is corresponding item in the ItemsSource :

<Button 
        .......
        Command="{Binding RelativeSource=
            {RelativeSource Mode=FindAncestor, 
            AncestorType={x:Type Window}}, 
            Path=DataContext.SendMessageCommand}"
        CommandParameter="{Binding FullCommandString}"/>