Binding with BasePage in Xamarin Forms - binding

Question

I am implementing a Xamarin app with FreshMVVM framework and I want to use a BasePage to share some code among Pages.
The problem is that when I need to bind some Properties in the MainPage.xaml I have to specify the Source in this way to make it working: Text="{Binding Title, Source={x:Reference mainPage}}". Otherwise without Source Binding doesn't work.
Ok, I get it but is this the right way? Is there another way to achieve the same result? What about when I have plenty of bindings in a page? For instance, is it possible "setting" the Source at un upper level, because in my opinion setting the same Source for each Binding is very annoying.
BasePage.xaml
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="TestXamarin.BasePage"
x:Name="basePage">
<ContentView>
<StackLayout Orientation="Vertical">
<Label Text="HEADER" FontSize="Large"/>
<Label Text="{Binding Text, Source={x:Reference basePage}}" FontSize="Large"/>
<ContentPresenter BindingContext="{Binding Parent.BindingContext}"
Content="{Binding PageContent, Source={x:Reference basePage}}" />
</StackLayout>
</ContentView>
</ContentPage>
BasePage.xaml.cs
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace TestXamarin
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class BasePage : ContentPage
{
public static readonly BindableProperty TextProperty = BindableProperty.Create(
nameof(Text),
typeof(string),
typeof(BasePage));
public string Text
{
get { return (string)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
public static readonly BindableProperty PageContentProperty = BindableProperty.Create(
nameof(PageContent),
typeof(object),
typeof(BasePage));
public object PageContent
{
get { return GetValue(PageContentProperty); }
set { SetValue(PageContentProperty, value); }
}
public BasePage()
{
InitializeComponent();
}
}
}
MainPage.xaml
<local:BasePage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:TestXamarin"
x:Class="TestXamarin.MainPage"
Text="FROM MAIN PAGE"
x:Name="mainPage">
<local:BasePage.PageContent>
<StackLayout>
<Label Text="Body" FontSize="Large"/>
<Label Text="{Binding Title, Source={x:Reference mainPage}}" FontSize="Large"/>
</StackLayout>
</local:BasePage.PageContent>
</local:BasePage>
MainPage.xaml.cs
public partial class MainPage : BasePage
{
public MainPage()
{
Title = "MAIN PAGE";
InitializeComponent();
}
}

Answer 1

Another way to achieve what you are trying to do would be with control templates.
Here I have defined a template in App.xaml
<ControlTemplate x:Key="ActivityIndicatorTemplate">
<Grid>
<ContentPresenter />
<StackLayout Style="{StaticResource BlockingPanel}"
IsVisible="{TemplateBinding BindingContext.IsBusy}">
<ActivityIndicator Style="{StaticResource ActivityIndicatorStyle}"
IsVisible="{TemplateBinding BindingContext.IsBusy}"
IsRunning="{TemplateBinding BindingContext.IsBusy}" />
</StackLayout>
</Grid>
</ControlTemplate>
Note the content presenter and the TemplateBinding.
I use it on a page like this.
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="Test.MyTestPage"
ControlTemplate="{StaticResource ActivityIndicatorTemplate}"
Title="{Binding Title}">
<Grid>
...
</Grid>
</ContentPage>
The page content replaces the content presenter in the template. Looks simpler than a base page.