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POCasting to templated classes from framework objects in C++/Cx
 

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    <p>I'm currently working on creating a new container in my WinRT project. This container will behave similar to a ListView, so I've decided to use similar names in its properties.</p> <p>I created a DependencyProperty for ItemsSource to mimic that of the built-in ItemsControl (abstract parent to other lists). ItemsControl defines ItemsSource as a <code>Platform::Object^</code>, so I did the same. This works fine.</p> <p>Later on, it's time to create items to go in the list, populate them with instances of the specified ItemsTemplate, and set their data contexts. This means I need to actually cast ItemsSource from <code>Platform::Object^</code> into something iterable. Unfortunately, to cast it to something iterable, I need to specify the templated type in the cast (e.g. <code>IIterable&lt;UIElement^&gt;^</code> or <code>IIterable&lt;Object^&gt;^</code>). At this stage, I don't particularly care what type of object it is because I'm just using it as the DataContext for the new list item, so casting to <code>IIterable&lt;Object^&gt;^</code> would be fine. Unfortunately, safe_cast doesn't let me do this unless the thing originally set to ItemsSource was also templated as a <code>IIterable&lt;Object^&gt;^</code> or some child such as <code>IVectorView&lt;Object^&gt;^</code>.</p> <p>With existing containers such as ListView, you can set the ItemsSource to a <code>Vector&lt;MyCustomViewModel^&gt;^</code> without first converting it to a <code>Vector&lt;Object^&gt;^</code> and it works just fine. So how do they do this? Are they not using safe_cast? I'm pretty sure using a less-safe cast would have adverse effects here. Have any other ideas?</p> <p><strong>TL;DR:</strong></p> <p>I have some <code>Platform::Object^</code> reference that I know points to an IIterable of other references. Is it possible to cast it to <code>IIterable&lt;Platform::Object^&gt;^</code> somehow, even if the iterable was originally created with some other template (such as <code>IIterable&lt;MyCustomViewModel^&gt;^</code>)?</p>
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