Selecting Current MenuItem in wpf - wpf

Question

How can I select the currentItem in a menuitem collection. Like one would do with a listbox. I tried wrapping the collection in a collectionViewSource, However that brought be no such luck.
Thanks in advance.

Answer 1

The MenuBase, which ContextMenu and Menu derive from, inherits ItemsControl, which does not include the concept of SelectedItem. That's something that ListBox adds.
You do, however, have the ItemsControl.ItemTemplate. Which is awesome.
One option would be to make your ItemTemplate a ToggleButton. This gives you a couple of things. Inherently, ToggleButtons can look like they're selected using their IsChecked property. Second, they have a Command property which you can bind to a command in your ViewModel.
So, if you have something along the lines of:
<Menu ItemsSource="{Binding ThingsToBindTo}">
<Menu.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.Resources>
<conv:BindingProxy x:Key="proxy" Data="{Binding}" />
</Grid.Resources>
<ToggleButton Content="{Binding NameOrLabel}" CommandParameter="{Binding}" Command="{Binding Path=DataContext.SelectThingCommand, RelativeSource={RelativeSource AncestorType=Menu}}" >
<ToggleButton.IsChecked>
<Binding Mode="OneWay" Path="DataContext.SelectedThing" RelativeSource={RelativeSource AncestorType=Menu}">
<Binding.Converter>
<conv:ComparisonConverter CompareTo="{Binding Source={StaticResource proxy}, Path=Data}" />
</Binding.Converter>
</Binding>
</ToggleButton.IsChecked>
</ToggleButton>
</Grid>
</DataTemplate>
</Menu.ItemTemplate>
</Menu>
So this is a little complicated.
As per normal, you're binding to a list of items. ThingsToBindTo should be whatever your list is. Then you start defining your template. NameOrLabel is whatever property you want to appear on your toggle button. The command parameter is binding to the data item that the template is wrapping around by using nothing more than "{Binding}". The command is actually on the DataContext of your Menu, which is why RelativeSource is used here.
What this is saying is you're going to pass a command the thing that was just clicked. Effectively, you're selecting the button you click. Then, your command just needs to set a SelectedThing property in your ViewModel equal to whatever Thing is passed to it. Hopefully you have implemented a class that implements ICommand to create your delegate commands. If you don't, there are a lot of articles out there on how to do it. If you don't know how, put a comment on this post and I'll add the source code to do it.
Then we have the "IsChecked" bad boy. We're actually doing a binding long-hand there. This is the more complicated piece, but it allows a DataTemplated item to actually bind to itself within a converter.
First, you need the proxy object, which is explained here:
http://tomlev2.wordpress.com/2011/03/21/wpf-how-to-bind-to-data-when-the-datacontext-is-not-inherited/
Very simple to implement. Once it is done, the BindingProxy resource within your grid will work, and can act as an anchor back to the item bound to by the DataTemplate. The linked article explains why.
Then, you need a converter that compares two objects to each other.
public class ComparisonConverter : DependencyObject, IValueConverter
{
public object CompareTo
{
get { return (object)GetValue(CompareToProperty); }
set { SetValue(CompareToProperty, value); }
}
public static readonly DependencyProperty CompareToProperty =
DependencyProperty.Register("CompareTo", typeof(object), typeof(ComparisonConverter), new UIPropertyMetadata(null));
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (CompareTo != null)
{
return CompareTo.Equals(value);
}
else
{
return false;
}
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
So now that binding will take the selected item from the DataContext of the menu, and compare it to whatever the ToggleButton is bound to. If the two objects match, the button appears clicked/selected. If they don't match, the button doesn't look selected.
So I do happen to have that BindingProxy and my converter in the same namespace. You don't necessarily have to do that. I just usually have a namespace for "Xaml Trick" classes that I have to program.
This is a lot to digest, and I'm happy to clarify anything.
One other thing...if you don't like the "ToggleButton" look, you can always style them to look completely different. The thing that having a ToggleButton buys you is the "IsChecked" property and the Command property. You can make the ContentTemplate look like anything you want, which gives you a lot of freedom in styling your menu.

Answer 2

If the ListBox has its ItemsSource set to a generic list of a complex entity, using ListBox.SelectedValue will get you the currently selected data.
For example:
public partial class NameListView : Window
{
/// <summary>
/// Constructor
/// </summary>
public NameListView()
{
List<string> names = new List<string>();
names.Add("John Doe");
names.Add("Jane Doe");
lbNameList.ItemsSource = names;
}
/// <summary>
/// Selection changed event handler for ListBox lbNameList
/// </summary>
void lbNameList_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (e.AddedItems.Count > 0)
{
string currentValue = lbNameList.SelectedValue.ToString();
MessageBox.Show("Currently selected value: " + currentValue);
}
}
}

Answer 3

If you have a property in your contextfile ( like Codebehind file or ViewModel ) that represents the currentSelectedItem then you can write the following in your xaml :
<ListView x:Name="MyList"
ItemsSource="MySource"
SelectedItem="{Binding Path=MyCurrentSelectedItem}" IsSynchronizedWithCurrentItem="True">
Codebehind / ViewModel
public MyType MyCurrentSelectedItem { get; set; }