WPF: Binding to a (observable) Dictionary - wpf

Question

I'm using this ObservableCollection-Class within my Project: Link
I want to Bind a RibbonMenuButton to a ObservableDictionary<string,bool>:
<r:RibbonMenuButton ItemsSource="{Binding MyDictionary}">
<r:RibbonMenuButton.ItemContainerStyle>
<Style TargetType="{x:Type r:RibbonMenuItem}">
<Setter Property="IsCheckable" Value="true"/>
<Setter Property="Header" Value="{Binding Path=Key}"/>
<Setter Property="IsChecked" Value="{Binding Path=Value}"/>
</style>
</r:RibbonMenuButton.ItemContainerStyle>
</r:RibbonMenuButton>
But I get exceptions because the Value-Properties of the internal IDictionary-KeyValuePairs are readonly. Any Idea how to solve this?
I thought about something like:
<Setter Property="IsChecked" Value="{Binding Source=MyDictionary[{Binding Path=Key}]}"/>
But this won't work 'cause of {Binding} in {Binding}...

Answer 1

This doesn't work, because your dictionary isn't treated as a dictionary but as an IEnumerable<KeyValuePair<string, bool>>. So each RibbonMenuItem is bound to a KeyValuePair<string, bool> with readonly properties Key and Value.
You can do two one things:
1. Use an ObservableCollection<Tuple<string, bool>> instead of the dictionary and bind IsChecked to Item2.
2. Create a little helper class that contains a IsChecked property and change your dictionary to contain that class as the value and bind IsChecked to Value.IsChecked.
I would go with answer two, because the needed changes and possible side effects are smaller.
My answer assumes that you want to have a two way binding on IsChecked. If not, go with the answer of slugster.

Answer 2

WPF binding is two-way by default. Make it one-way and see if that solves your issue.
<r:RibbonMenuButton ItemsSource="{Binding MyDictionary}">
<r:RibbonMenuButton.ItemContainerStyle>
<Style TargetType="{x:Type r:RibbonMenuItem}">
<Setter Property="IsCheckable" Value="true"/>
<Setter Property="Header" Value="{Binding Key, Mode=OneWay}"/>
<Setter Property="IsChecked" Value="{Binding Value, Mode=OneWay}"/>
</style>
</r:RibbonMenuButton.ItemContainerStyle>
</r:RibbonMenuButton>
Here is a reference for you: MSDN Windows Presentation Foundation Data Binding: Part 1 (specifically check the section Binding Mode close to the bottom of the page)

Answer 3

If You want to bind MenuItems to Dictionary<string, bool> without using a helper class, like the accepted answer suggests, here is the minimal-change solution (no need to add anything else):
define a Click event inside the ItemContainerStyle whose ClickEventHandler will update the dicitonary.
declare a dictionary and initialize it inside the UserControl's / Window's constructor
In code:
MainWindow.xaml:
<MenuItem Header="_My settings" ItemsSource="{Binding MySettings}">
<MenuItem.ItemContainerStyle>
<Style TargetType="{x:Type MenuItem}">
<Setter Property="IsCheckable" Value="true"/>
<Setter Property="Header" Value="{Binding Key, Mode=OneWay}"/>
<Setter Property="IsChecked" Value="{Binding Value, Mode=OneWay}"/>
<!-- this is the main line of code -->
<EventSetter Event="Click" Handler="MySettings_ItemClick"/>
</Style>
</MenuItem.ItemContainerStyle>
</MenuItem>
MainWindow.xaml.cs:
public partial class MainWindow : Window
{
// properties...
// Declaration of the dictionary
public Dictionary<string, bool> MySettings{ get; set; }
public MainWindow()
{
InitializeComponent();
// Initialize the dictionary
MySettings = new Dictionary<string, bool>()
{
{ "SettingOne", true}
// Other pairs..
};
}
// other things..
// ClickEvent hanlder
private void MySettings_ItemClick(object sender, RoutedEventArgs e)
{
MenuItem clickedItem = (sender as MenuItem);
MySettings[clickedItem.Header as string] = clickedItem.IsChecked;
}
} // end of MainWindow class
That's it! You're all set!
Credits to slugster and his answer for XAML code for OneWay binding :)

Answer 4

As a general solution to this problem of binding to dictionaries I created an UpdateableKeyValuePair and return that instaed of the usual KeyValuePair. Here is my class:
public class UpdateableKeyValuePair<TKey,TValue>
{
private IDictionary<TKey, TValue> _owner;
private TKey _key;
public UpdateableKeyValuePair(IDictionary<TKey, TValue> Owner, TKey Key_)
{
_owner = Owner;
_key = Key_;
}
public TKey Key
{
get
{
return _key;
}
}
public TValue Value
{
get
{
return _owner[_key];
}
set
{
_owner[_key] = value;
}
}
}