Question

I have class, that selects the ItemDataTemplate for objects. But I can’t reference it in my XAML code. (Page.Resources).

It’s the Items page in XAML. The class is in the commons folder, and I’ve referenced the commons folder here:

xmlns:common="using:Sample_App.Common"

and then when I wan’t to add it to my XAML:

<common:MyDataTemplateSelector x:Key="Selector" AdTemplate="{StaticResource Ad}" NormalTemplate="{StaticResource Normal}"></common:MyDataTemplateSelector>

I get the following error:

The name “MyDataTemplateSelector” does not exist in the namespace “using:MyDataSelector”

Here’s the MyDataSelector class:

namespace MyDataSelector
{
    private class MyDataTemplateSelector : DataTemplateSelector
    {
        public DataTemplate NormalTemplate { get; set; }

        public DataTemplate AdTemplate{ get; set; }

        protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
        {
            if (item is TestApp.Mainpage.NormalData)
                return NormalTemplate
            if (item is TestApp.Mainpage.AdData)
                return AdTemplate;

            return SelectTemplateCore(item, container);
        }
    }
}

Answer 1

You have a couple problems with your code. First of all, you mention that your class is in “the commons folder” – this is totally irrelevant. The location of a code file generally doesn’t matter to the compiler, but the namespace you declare the class in does matter.

namespace MyDataSelector // <- This is where your class can be found
{
    private class MyDataTemplateSelector : DataTemplateSelector
    {

So since your class is in the namespace MyDataSelector, the reference in your xaml files should look something like this:

<Page x:Class="WpfApplication1.Page1"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:myDataSelector="using:MyDataSelector">

And you would reference your class like this:

<myDataSelector:MyDataTemplateSelector />

Another issue is that your class is declared as private. That doesn’t make sense and probably won’t compile. Remove private to make your class internal, or change it to public.