Example for Shift+Click or Control+Click button?

[derekantrican]

Is there an example for shift+clicking or ctrl+clicking a button? I want my button to have one command, but if I shift+click the button I want it to invoke a different command

[wieslawsoltes]

I don't know any built-in way to do that.

I suppose one can create custom action based on InvokeCommandAction for button with check for key gesture.

[wieslawsoltes]

@derekantrican

Custom behavior for your use case (will be available in next release under Avalonia.Xaml.Interactions.Custom namespace as ButtonClickEventTriggerBehavior from Avalonia.Xaml.Interactions NuGet package.

ButtonClickEventTriggerBehavior.cs

using Avalonia.Controls;
using Avalonia.Input;
using Avalonia.Interactivity;
using Avalonia.Xaml.Interactivity;

namespace Avalonia.Xaml.Interactions.Custom
{
    /// <summary>
    /// A behavior that listens for a <see cref="Button.ClickEvent"/> event on its source and executes its actions when that event is fired.
    /// </summary>
    public class ButtonClickEventTriggerBehavior : Trigger<Button>
    {
        private KeyModifiers _savedKeyModifiers = KeyModifiers.None;

        /// <summary>
        /// Identifies the <seealso cref="KeyModifiers"/> avalonia property.
        /// </summary>
        public static readonly StyledProperty<KeyModifiers> KeyModifiersProperty =
            AvaloniaProperty.Register<ButtonClickEventTriggerBehavior, KeyModifiers>(nameof(KeyModifiers));

        /// <summary>
        /// Gets or sets the required key modifiers to execute <see cref="Button.ClickEvent"/> event handler. This is a avalonia property.
        /// </summary>
        public KeyModifiers KeyModifiers
        {
            get => GetValue(KeyModifiersProperty);
            set => SetValue(KeyModifiersProperty, value);
        }

        /// <summary>
        /// Called after the behavior is attached to the <see cref="Behavior.AssociatedObject"/>.
        /// </summary>
        protected override void OnAttached()
        {
            base.OnAttached();

            if (AssociatedObject is { })
            {
                AssociatedObject.Click += AssociatedObject_OnClick;
                AssociatedObject.AddHandler(InputElement.KeyDownEvent, Button_OnKeyDown, RoutingStrategies.Tunnel);
                AssociatedObject.AddHandler(InputElement.KeyUpEvent, Button_OnKeyUp, RoutingStrategies.Tunnel);
            }
        }

        /// <summary>
        /// Called when the behavior is being detached from its <see cref="Behavior.AssociatedObject"/>.
        /// </summary>
        protected override void OnDetaching()
        {
            base.OnDetaching();

            if (AssociatedObject is { })
            {
                AssociatedObject.Click -= AssociatedObject_OnClick;
                AssociatedObject.RemoveHandler(InputElement.KeyDownEvent, Button_OnKeyDown);
                AssociatedObject.RemoveHandler(InputElement.KeyUpEvent, Button_OnKeyUp);
            }
        }

        private void AssociatedObject_OnClick(object sender, RoutedEventArgs e)
        {
            if (AssociatedObject is { } && KeyModifiers == _savedKeyModifiers)
            {
                Interaction.ExecuteActions(AssociatedObject, Actions, e);
            }
        }

        private void Button_OnKeyDown(object sender, KeyEventArgs e)
        {
            _savedKeyModifiers = e.KeyModifiers;
        }

        private void Button_OnKeyUp(object sender, KeyEventArgs e)
        {
            _savedKeyModifiers = KeyModifiers.None;
        }
    }
}

Example usage:

<UserControl x:Class="BehaviorsTestApplication.Views.Pages.ButtonClickEventTriggerBehaviorView"
             xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:i="using:Avalonia.Xaml.Interactivity"
             xmlns:ia="using:Avalonia.Xaml.Interactions.Core"
             xmlns:ic="using:Avalonia.Xaml.Interactions.Custom"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d" d:DesignWidth="600" d:DesignHeight="450">
    <Grid RowDefinitions="*,Auto" ColumnDefinitions="30*,5,30*,5,30*">
        <Canvas Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="5" Margin="5" Background="{DynamicResource GrayBrush}">
            <Ellipse Canvas.Left="{Binding Position, Mode=TwoWay}" Canvas.Top="200" Fill="{DynamicResource RedBrush}" Stroke="{DynamicResource YellowBrush}" StrokeThickness="5" Height="100" Width="100"/>
        </Canvas>
        <Button x:Name="MoveLeftButton" Content="Move Left (Hold Control)" Grid.Row="1" Grid.Column="0" Margin="5,0,0,5">
            <i:Interaction.Behaviors>
                <ic:ButtonClickEventTriggerBehavior KeyModifiers="Control">
                    <ia:InvokeCommandAction Command="{Binding MoveLeftCommand}"/>
                </ic:ButtonClickEventTriggerBehavior>
            </i:Interaction.Behaviors>
        </Button>
        <Button x:Name="ResetMoveButton" Content="Reset Move (Hold Control+Shift)" Grid.Row="1" Grid.Column="2" Margin="0,0,0,5">
            <i:Interaction.Behaviors>
                <ic:ButtonClickEventTriggerBehavior KeyModifiers="Control,Shift">
                    <ia:InvokeCommandAction Command="{Binding ResetMoveCommand}"/>
                </ic:ButtonClickEventTriggerBehavior>
            </i:Interaction.Behaviors>
        </Button>
        <Button x:Name="MoveRightButton" Content="Move Right (Hold Shift)" Grid.Row="1" Grid.Column="4" Margin="0,0,5,5">
            <i:Interaction.Behaviors>
                <ic:ButtonClickEventTriggerBehavior KeyModifiers="Shift">
                    <ia:InvokeCommandAction Command="{Binding MoveRightCommand}"/>
                </ic:ButtonClickEventTriggerBehavior>
            </i:Interaction.Behaviors>
        </Button>
    </Grid>
</UserControl>

You can combine multiple triggers under one button behaviors collection:

        <Button Content="Left (Control), Reset (Hold Control+Shift), Right (Hold Shift)" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="5" Margin="5,0,0,5">
            <i:Interaction.Behaviors>
                <ic:ButtonClickEventTriggerBehavior KeyModifiers="Control">
                    <ia:InvokeCommandAction Command="{Binding MoveLeftCommand}"/>
                </ic:ButtonClickEventTriggerBehavior>
                <ic:ButtonClickEventTriggerBehavior KeyModifiers="Shift">
                    <ia:InvokeCommandAction Command="{Binding ResetMoveCommand}"/>
                </ic:ButtonClickEventTriggerBehavior>
                <ic:ButtonClickEventTriggerBehavior KeyModifiers="Control,Shift">
                    <ia:InvokeCommandAction Command="{Binding MoveRightCommand}"/>
                </ic:ButtonClickEventTriggerBehavior>
            </i:Interaction.Behaviors>
        </Button>

[derekantrican]

Excellent - those code samples helped me get up and running!

Just to let you know, using the xmlns:i="using:Avalonia.Xaml.Interactivity" gave me the error "Unable to resolve type Interaction from namespace using:Avalonia.Xaml.Interactivity" but changing it to xmlns:i="clr-namespace:Avalonia.Xaml.Interactivity;assembly=Avalonia.Xaml.Interactivity" seemed to work

[wieslawsoltes]

Excellent - those code samples helped me get up and running!

Just to let you know, using the xmlns:i="using:Avalonia.Xaml.Interactivity" gave me the error "Unable to resolve type Interaction from namespace using:Avalonia.Xaml.Interactivity" but changing it to xmlns:i="clr-namespace:Avalonia.Xaml.Interactivity;assembly=Avalonia.Xaml.Interactivity" seemed to work

That sometime happens in previewer when assembly is not loaded so your solution is correct.