Displaying read only properties in PropertyGrid control

Question

I am using the WPF Extended Toolkit to display the properties of a Team object. Now one of these properties is a collection Persons. No problem I get a nice drop down, which when I click on shows me the names and ages of each of these people.

Now the problem is that I don't actually want to expose my Collection as public. However as soon as I make its setter private the property is disabled preventing the user from seeing the Person collection and the person details:

How should I display my Person Collection when its setter is private? Can I do this with a XAML template? If so how? I'm using MVVM so I don't want to put anything in the code behind.

Update

OK so the solution by @tencntraze got me most of the way there - thanks. However it doesn't work for Collections of objects which is what I've got in my case. In addition it can also be simplified to use the CollectionControlDialog instead of the custom ReadOnlyCollectionViewer that's been implemented below.

XAML

<UserControl x:Class="DevExpressTreeList.ReadOnlyCollectionEditor"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Name="MyUserControl"
             >
    <DockPanel>
        <Button Click="Button_OnClick" DockPanel.Dock="Right">
            <Label Content="˅" Padding="2,0,2,0" />
        </Button>
        <Label Name="CollectionLabel" Content="(Collection)" Padding="2,2,2,0" />
    </DockPanel>
</UserControl>

Code-Behind

public partial class ReadOnlyCollectionEditor : UserControl, ITypeEditor
{
    public ReadOnlyCollectionEditor()
    {
        InitializeComponent();
    }

    // Use typeof(object) to allow for any Collection<T>
    public static readonly DependencyProperty ValueProperty = DependencyProperty.Register(
        "Value", typeof(object), typeof(ReadOnlyCollectionEditor), new PropertyMetadata(default(object)));

    public object Value
    {
        // We are now using object so no need to cast
        get { return GetValue(ValueProperty); }
        set { SetValue(ValueProperty, value); }
    }

    public FrameworkElement ResolveEditor(Xceed.Wpf.Toolkit.PropertyGrid.PropertyItem propertyItem)
    {
        var binding = new Binding("Value")
        {
            Source = propertyItem,
            Mode = propertyItem.IsReadOnly ? BindingMode.OneWay : BindingMode.TwoWay
        };
        BindingOperations.SetBinding(this, ValueProperty, binding);
        return this;
    }

    private void Button_OnClick(object sender, RoutedEventArgs e)
    {
        var collectionControlDialog = new CollectionControlDialog
        {
            ItemsSource = (IList)this.Value
        };
        collectionControlDialog.ShowDialog();
    }
}

Answer 1

I think that your best bet here is to implement your own editor, as per the Xceed Documentation. You are then able to provide whatever UI you would like to display to the user without needing to commit the values back to the underlying object. Note that this approach works for both private setters as well as properties without any setter.

ReadOnlyCollectionEditor

XAML

<UserControl x:Class="WpfApplication2.ReadOnlyCollectionEditor"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Name="uc">
    <Button Click="Button_OnClick" Height="20" />
</UserControl>

Code-Behind

public partial class ReadOnlyCollectionEditor : UserControl, ITypeEditor
{
    public ReadOnlyCollectionEditor()
    {
        InitializeComponent();
    }

    public static readonly DependencyProperty ValueProperty = DependencyProperty.Register(
        "Value", typeof (IList<string>), typeof (ReadOnlyCollectionEditor), new PropertyMetadata(default(IList<string>)));

    public IList<string> Value
    {
        get { return (IList<string>)GetValue(ValueProperty); }
        set { SetValue(ValueProperty, value); }
    }

    public FrameworkElement ResolveEditor(Xceed.Wpf.Toolkit.PropertyGrid.PropertyItem propertyItem)
    {
        var binding = new Binding("Value")
        {
            Source = propertyItem,
            Mode = propertyItem.IsReadOnly ? BindingMode.OneWay : BindingMode.TwoWay
        };
        BindingOperations.SetBinding(this, ValueProperty, binding);
        return this;
    }

    private void Button_OnClick(object sender, RoutedEventArgs e)
    {
        ReadOnlyCollectionViewer viewer = new ReadOnlyCollectionViewer {DataContext = this};
        viewer.ShowDialog();
    }
}

ReadOnlyCollectionViewer

<Window x:Class="WpfApplication2.ReadOnlyCollectionViewer"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="ReadOnlyCollectionViewer" Height="300" Width="300">
    <ListBox ItemsSource="{Binding Value}" />
</Window>

Sample Properties Class

public class MyDataObjects
{
    public MyDataObjects()
    {
        this.CollectionProperty = new Collection<string> {"Item 1", "Item 2", "Item 3"};            
        this.StringProperty = "Hi!";
    }

    public string StringProperty { get; set; }

    [Editor(typeof(ReadOnlyCollectionEditor), typeof(ReadOnlyCollectionEditor))]
    public ICollection<string> CollectionProperty { get; private set; } 
}   

Assigning to the property grid

this.propertyGrid.SelectedObject = new MyDataObjects();

Results

EDIT

I realize that you want to use MVVM, which I strongly encourage when using WPF, but for purposes of this sample I believe that keeping it simple helps illustrate the point, otherwise it brings up other questions like showing a modal dialog from MVVM, so I'm just showing the dialog with a button click.

Answer 2

public Collection<Person> People
{
    get { return _people; }
    set { throw new NotSupportedException(); }
}

Perhaps not the nicest solution but it will work with the PropertyGrid while preventing users setting a new collection.