Property Resources is null or is not IEnumerable - xaml

Question

I got this error in break mode in visual studio 2015 when I was learning to make a Xamarin.Forms page.
Unhandled Exception:
Xamarin.Forms.Xaml.XamlParseException: Position 12:10. Property Resources is null or is not IEnumerable
My App.xaml code is below
<?xml version="1.0" encoding="utf-8" ?>
<Application xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="Bisells.App">
<Application.Resources>
<!-- Application resource dictionary -->
<!-- colors -->
<!--<Color x:Key="HeaderTextColor">#585858</Color>
<Color x:Key="BodyTextColor">#C3C3C3</Color>-->
<Color x:Key="TimelineColor">#E4B6C3</Color>
<Color x:Key="HeaderTextColor">#3C3C3C</Color>
<Color x:Key="BodyTextColor">#869EAC</Color>
<Color x:Key="TimeColor">#A64C79</Color>
<!-- font families -->
<OnPlatform
x:Key="RegularFontFamily"
x:TypeArguments="x:String"
Android="sans-serif"
iOS="HelveticaNeue" />
<OnPlatform
x:Key="LightFontFamily"
x:TypeArguments="x:String"
Android="sans-serif-light"
iOS="HelveticaNeue-Light" />
<OnPlatform
x:Key="MediumFontFamily"
x:TypeArguments="x:String"
Android="sans-serif-medium"
iOS="HelveticaNeue-Medium" />
<!-- fonts -->
<Font
x:Key="HeaderFont"
FontFamily="{StaticResource MediumFontFamily}"
FontSize="30" />
<Font
x:Key="SubHeaderFont"
FontFamily="{StaticResource MediumFontFamily}"
FontSize="18" />
<Font
x:Key="TitleFont"
FontFamily="{StaticResource MediumFontFamily}"
FontSize="20" />
<Font
x:Key="BodyFont"
FontFamily="{StaticResource RegularFontFamily}"
FontSize="18" />
<!-- styles -->
<Style x:Key="PageHeaderLabel" TargetType="Label">
<Setter Property="TextColor" Value="{StaticResource HeaderTextColor}" />
<Setter Property="Font" Value="{StaticResource HeaderFont}" />
</Style>
<Style x:Key="SubHeaderLabel" TargetType="Label">
<Setter Property="TextColor" Value="{StaticResource BodyTextColor}" />
<Setter Property="Font" Value="{StaticResource SubHeaderFont}" />
</Style>
<Style x:Key="ClassTimeLabel" TargetType="Label">
<Setter Property="TextColor" Value="{StaticResource TimeColor}" />
<Setter Property="Font" Value="{StaticResource TitleFont}" />
</Style>
<Style x:Key="ClassNameLabel" TargetType="Label">
<Setter Property="TextColor" Value="{StaticResource HeaderTextColor}" />
<Setter Property="Font" Value="{StaticResource TitleFont}" />
</Style>
<Style x:Key="ClassInstructorLabel" TargetType="Label">
<Setter Property="TextColor" Value="{StaticResource BodyTextColor}" />
<Setter Property="Font" Value="{StaticResource BodyFont}" />
</Style>
</Application.Resources>
</Application>
Also xamarin not showing where exactly the exception occuring

Answer 1

You forgot the ResourceDictionary tag:
<Application.Resources>
<ResourceDictionary>
<!-- Application resource dictionary -->
<!-- colors -->
<!--<Color x:Key="HeaderTextColor">#585858</Color>
<Color x:Key="BodyTextColor">#C3C3C3</Color>-->
<Color x:Key="TimelineColor">#E4B6C3</Color>
<Color x:Key="HeaderTextColor">#3C3C3C</Color>
<Color x:Key="BodyTextColor">#869EAC</Color>
<Color x:Key="TimeColor">#A64C79</Color>
</ResourceDictionary>
</Application.Resources>

Answer 2

Define style in App.xaml like this:
<Application xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="PlatformFontSample.App">
<Application.Resources>
<ResourceDictionary>
<OnPlatform x:Key="FontFamilyName" x:TypeArguments="x:String" iOS="MarkerFelt-Thin" Android="OpenSans" WinPhone="Segoe UI" />
<Style x:Key="FontLabel" TargetType="Label">
<Setter Property="FontFamily" Value="{DynamicResource FontFamilyName}" />
</Style>
</ResourceDictionary>
</Application.Resources>
and then Use in xaml:
<Label Text="{Binding Name}" Style="{DynamicResource FontLabel}" FontSize="Medium" FontAttributes="Bold" LineBreakMode="NoWrap"/>