如何在WPF中的DataTemplateSelector类中查找UserControl中的资源？

Question

I'm creating my own UserControl and I have two different DataTemplates under the UserControl.Resources section in my XAML. I want to choose between these two datatemplates depending on the value of a property on objects displayed in a listview. I do this by creating a custom DataTemplateSelector class and overriding the SelectTemplate method which is supposed to return the DataTemplate I wish to use. However, I have no idea how to "find" my datatemplates that are located in the UserControls resource section, all the examples I've seen only fetches datatemplates from Window.Resources . In this example they fetch the current MainWindow and then use FindResource to find the DataTemplate , how do I fetch my UserControl in a similar manner?:

public override DataTemplate 
            SelectTemplate(object item, DependencyObject container)
        {
            if (item != null && item is AuctionItem)
            {
                AuctionItem auctionItem = item as AuctionItem;
                Window window = Application.Current.MainWindow;

                switch (auctionItem.SpecialFeatures)
                {
                    case SpecialFeatures.None:
                        return 
                            window.FindResource("AuctionItem_None") 
                            as DataTemplate;
                    case SpecialFeatures.Color:
                        return 
                            window.FindResource("AuctionItem_Color") 
                            as DataTemplate;
                }
            }

            return null;
        }

The example above is from here: ItemsControl.ItemTemplateSelector Property

Answer 1

Try this:

    public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        if (item != null && item is AuctionItem)
        {
            AuctionItem auctionItem = item as AuctionItem;

            switch (auctionItem.SpecialFeatures)
            {
                case SpecialFeatures.None:
                    return 
                        ((FrameworkElement)container).FindResource("AuctionItem_None") 
                        as DataTemplate;
                case SpecialFeatures.Color:
                    return 
                        ((FrameworkElement)container).FindResource("AuctionItem_Color") 
                        as DataTemplate;
            }
        }

        return null;
    }

Answer 2

I usually instantiate my DataTemplateSelector from code behind with the UserControl as parameter in the constructor of the DataTemplateSelector, like so:

public class MyUserControl : UserControl
{
    public MyUserControl()
    {
        Resources["MyDataTemplateSelector"] = new MyDataTemplateSelector(this);
        InitializeComponent();
    }
}

public class MyDataTemplateSelector : DataTemplateSelector
{
    private MyUserControl parent;
    public MyDataTemplateSelector(MyUserControl parent)
    {
        this.parent = parent;
    }

    public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        parent.DoStuff();
    }
}

Not the most prettiest girl in town, but it get the job done ;)

Hope this helps!

Answer 3

       <DataTemplate x:Key="addTemplate">
        <Button Command="{Binding Path=AddCommand}">Add</Button>
    </DataTemplate>

    <DataTemplate x:Key="editTemplate">
        <Button Command="{Binding Path=UpdateCommand}">Update</Button>
    </DataTemplate>

    <TemplateSelectors:AddEditTemplateSelector
        AddTemplate="{StaticResource addTemplate}"
        EditTemplate="{StaticResource editTemplate}"
        x:Key="addEditTemplateSelector" />

XAML only!

Answer 4

A WinRT & Windows Phone solution involves moving up the visual tree until the parent control is found:

    protected override Windows.UI.Xaml.DataTemplate SelectTemplateCore(object item, Windows.UI.Xaml.DependencyObject container)
    {
        var parent = FindParent<MyParentControlType>(container as FrameworkElement);

        if(parent != null)
        {
            if (item is Something)
                return parent.Resources["TemplateForSomething"] as DataTemplate;
            else if(item is SomethingElse)
                return parent.Resources["TemplateForSomethingElse"] as DataTemplate;
            else 
                // etc
        }
        else
        {
            return App.Current.Resources["SomeFallbackResource"] as DataTemplate;
        }
    }

    public static T FindParent<T>(FrameworkElement element) where T : FrameworkElement
    {
        FrameworkElement parent = Windows.UI.Xaml.Media.VisualTreeHelper.GetParent(element) as FrameworkElement;

        while (parent != null)
        {
            T correctlyTyped = parent as T;

            if (correctlyTyped != null)
                return correctlyTyped;
            else
                return FindParent<T>(parent);
        }

        return null;
    }

The FindParent method is based on the accepted answer here: How to get a ListView from a ListViewItem?