StaticResourceExtension as property element in Visual Studio 2015 - xaml

Question

I have the next XAML:
<ContentPage ...>
<ContentPage.Resources>
<ResourceDictionary>
<Style x:Key="visualStyle" TargetType="VisualElement">
<Setter Property="BackgroundColor" Value="Red" />
</Style>
<Style x:Key="baseStyle" TargetType="View" BasedOn="{StaticResource visualStyle}">
...
</Style>
<Style x:Key="labelStyle" TargetType="Label" BasedOn="{StaticResource baseStyle}">
<Setter Property="TextColor" Value="Black" />
</Style>
</ResourceDictionary>
</ContentPage.Resources>
<ContentPage.Style>
<StaticResourceExtension Key="visualStyle" />
</ContentPage.Style>
...
</ContentPage>
When I try to set Style for entire ContentPage using visualStyle StaticResourceExtension I get the next annoing popup in Visual Studio:
Why is this happening and how to remove it? XAML is correct and is successfully parsed in runtime.

Answer 1

That's a very unusual syntax to be using. Markup extensions are almost always instantiated using moustache bracket syntax, so it doesn't surprise me that the Intellisense is getting confused.
I see why you are doing this though - you want to reference a resource that is defined within the Resources of the referencing element. But XAML wants to be able to parse that resource before encountering the reference.
There are a few options...
You could move the visualStyle resource to App.xaml and reference it from your page using normal attribute plus moustache bracket syntax.
You could reference it via DynamicResource instead, which should allow it to resolve properly. But this seems a little heavy-handed.
However, my preferred solution is the first one since this is likely an application-wide thematic style.

Answer 2

I see this part of your code, and wonder (since I'm too starting to learn Xamarin) couldn't it be that the StaticResourceExtension key attribute, must be used with the suffix x:?
<ContentPage.Style>
<StaticResourceExtension x:Key="visualStyle" />
<!-- INSTEAD OF <StaticResourceExtension Key="visualStyle" />-->
</ContentPage.Style>
I just came across this exception and found that the problem was that I was using the attributes the wrong way, so maybe that exception is Xamarin's way to tell us that we messed up on something, without saying explicitly on what.