WPF - Binding in custom ComboBox

Question

I'm trying to create a custom combobox that have a list of items, and each item have an add(+) button that is suppose to add that item to a "favorite" list:

XAML:

<UserControl x:Class=ComboBoxWithButton"
             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" 
             mc:Ignorable="d" d:DesignWidth="300" Height="25">
    <ComboBox 
    x:Name="ComboBoxBtn" 
    VerticalAlignment="Top" 
    HorizontalAlignment="Left" 
    Margin="0,0,0,-1" 
    Width="300" 
    ItemsSource="{Binding Source, RelativeSource={RelativeSource AncestorType=UserControl}}"
    SelectedItem="{Binding Path=Selected, Mode=TwoWay, RelativeSource={RelativeSource AncestorType=UserControl}}">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Label Content="{Binding}" Width="250" />
                    <Button Grid.Column="1" Command="{Binding CommandButton}"
                            CommandParameter="{Binding Path=Selected}">+</Button>
                </Grid>
            </DataTemplate>
        </ComboBox.ItemTemplate>
    </ComboBox>
</UserControl>

XAML.CS:

public IEnumerable Source
        {
            get { return (IEnumerable)GetValue(SourceProperty); }
            set { SetValue(SourceProperty, value); }
        }



    public static readonly DependencyProperty SourceProperty =
        DependencyProperty.Register("Source", typeof(IEnumerable), typeof(ComboBoxWithButton), new PropertyMetadata(null));


public static readonly DependencyProperty CommandProperty =
            DependencyProperty.Register("CommandButton", typeof(ICommand), typeof(ComboBoxWithButton), new PropertyMetadata(null));

        public ICommand CommandButton
        {
            get { return (ICommand)GetValue(CommandProperty); }
            set { SetValue(CommandProperty, value); }
        }

Then on my main view, using the combobox I have:

<controls:ComboBoxWithButton Source="{Binding AvailableClients}" Selected="{Binding SelectedClient, Mode=TwoWay}"
                                                       LostFocus="OnClientSelected"
                                                         CommandButton="{Binding AddFavoriteCommand}"/>

And:

AddFavoriteCommand = new RelayCommand<object>(AddToFavorite, f => true);

But it's not triggering my function "AddToFavorite"

That was something that I saw in a response here. But maybe is not correct. Source is a dependecy proprety yes — Andre Roque
– Andre Roque, Commented Oct 3, 2016 at 10:05
Added the lines that you asked. Just let me say that I guess the source is not the problem because the items are listed correctly. The problem is when I hit the button doesn't trigger the Comand/Action — Andre Roque
– Andre Roque, Commented Oct 3, 2016 at 10:14
I edited and deleted that part, as I said is something that I saw in another case and it was a test (that didn't work) — Andre Roque
– Andre Roque, Commented Oct 3, 2016 at 10:19

Ateik · Accepted Answer · 2016-10-03 14:42:34Z

1

The button is inside a DataTemplate, so each button's DataContext is different than the UserControl's DataContext.

You need to change the Command binding to access the UserControl's DataContext:

    <DataTemplate>
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="Auto" />
            </Grid.ColumnDefinitions>
            <Label Content="{Binding}" Width="250" />
            <Button Grid.Column="1" Command="{Binding CommandButton, RelativeSource={RelativeSource AncestorType=UserControl}}"
                    CommandParameter="{Binding Path=Selected}">+</Button>
        </Grid>
    </DataTemplate>

answered Oct 3, 2016 at 14:42

Ateik

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