Use custom base class for ContentPage in Xamarin.Forms

I want to use a custom ContentPage for my pages in Xamarin.Forms. I tried creating a custom class and specify the page in xaml like this: ``` <local:ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:XamarinFormsApp.Controls" x:Class="XamarinFormsApp.Views.WelcomeView"> <Label Text="{Binding MainText}" VerticalOptions="Center" HorizontalOptions="Center" /> </local:ContentPage> ``` This would (normally) work in xaml, but gives me this error in Xamarin.Forms: ``` Error 7 The "XamlG" task failed unexpectedly. System.Exception: Can't load types from xmlns clr-namespace:XamarinFormsApp.Controls at Xamarin.Forms.Build.Tasks.XamlG.GetNamespace(String namespaceuri) at Xamarin.Forms.Build.Tasks.XamlG.GetType(String nsuri, String type, IList`1 typeArguments, Func`2 getNamespaceOfPrefix) at Xamarin.Forms.Build.Tasks.XamlG.GenerateFile(String xamlFile, String outFile) at Xamarin.Forms.Build.Tasks.XamlG.Execute() at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__20.MoveNext() XamarinFormsApp.iOS ``` Is this (yet) unsupported or am I doing something wrong?