Error after installing Xamarin.Forms 3.0

I have installed Xamarin.Forms 3.0 and i have this message in debug in the App.xaml

"System.MissingMethodException: System.Func`2<string, string> Xamarin.Forms.Internals.ResourceLoader.get_ResourceProvider()"

in this piece of code

[global::Xamarin.Forms.Xaml.XamlFilePathAttribute("App.xaml")]
public partial class App : global::Xamarin.Forms.Application {

    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Xamarin.Forms.Build.Tasks.XamlG", "2.0.0.0")]
    private void InitializeComponent() {
        global::Xamarin.Forms.Xaml.Extensions.LoadFromXaml(this, typeof(App));
    }

Someone can help me to understand why?