Passing a dictionary to a behavior

Question

I have a simple Behavior like that

public class KeyBoardChangeBehavior : Behavior<UserControl>
{
    public Dictionary<string, int> DataToCheckAgainst; 


    protected override void OnAttached()
    {
        AssociatedObject.KeyDown += _KeyBoardBehaviorKeyDown;
    }

    protected override void OnDetaching()
    {
        AssociatedObject.KeyDown -= _KeyBoardBehaviorKeyDown;
    }


        void _KeyBoardBehaviorKeyDown(object sender, KeyEventArgs e)
    {
        // My business will go there 
    }

}

I want to asign value to this dictionary from the view , I call it as following

<UserControl x:Class="newhope2.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:Interactivity="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
             xmlns:Behaviors="clr-namespace:newhope2"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">

    <Interactivity:Interaction.Behaviors>
        <Behaviors:KeyBoardChangeBehavior  />
    </Interactivity:Interaction.Behaviors>

    <Grid x:Name="LayoutRoot" Background="White">

    </Grid>
</UserControl>

but how can I pass this dictionary to the behavior from XAML or its code behind

Answer 1

To take a Binding, a property needs to be a DependencyProperty.

You need to define the property, in the Behaviour, like so:

    public Dictionary<string, int> DataToCheckAgainst
    {
        get { return (Dictionary<string, int>)GetValue(DataToCheckAgainstProperty); }
        set { SetValue(DataToCheckAgainstProperty, value); }
    }

    public static readonly DependencyProperty DataToCheckAgainstProperty =
        DependencyProperty.Register(
            "DataToCheckAgainst",
            typeof(Dictionary<string, int>),
            typeof(KeyBoardChangeBehavior),
            new PropertyMetadata(null));

Use the Visual Studio "propdp" snippet.

Usage is as Adi said, like so:

<Interactivity:Interaction.Behaviors>
    <Behaviors:KeyBoardChangeBehavior DataToCheckAgainst="{Binding MyDictionary}" />
</Interactivity:Interaction.Behaviors>

Answer 2

All you need to do is declare the dictionary as a property and then pass it a value via binding.

In the behavior:

public Dictionary<string, int> DataToCheckAgainst { get; set; }

In XAML:

<Interactivity:Interaction.Behaviors>
    <Behaviors:KeyBoardChangeBehavior DataToCheckAgainst="{Binding MyDictionary}" />
</Interactivity:Interaction.Behaviors>