Xamarin C# Double Binding Source

Question

Is it possible to have 2 sources of binding? from an element such as CellView?

I searched and tried several possibilities I had in my mind without be able to do what I want to do. It seems so simple however..

Let says I have this page (I put a simple code, it is just a bit long, but not hard):

MainPage.cs

public partial class CoursesHistory : ContentPage
{
    // Course it's the element "data template" for the listView
    private class Course
    {
        public string Date { get; set; }
        public string Destination { get; set; }

        private string _price;
        public string Price {
            get { return this._price; }
            set
            {
                this._price = "€" + value;
            }
        }
    }

    // FontAttribute it's the other element which is not set as ItemsSource, but used from the cell to get the FontFamily ask, the FontSize etc 
    private class FontAttributes
    {
        public string MOON_FAMILY_ALIEN_BOLD { get; set; }
        ....

        public FontAttributes()
        {
            ....
        }
    }
    public FontAttributes FontAttr;

    public CoursesHistory()
    {
        FontAttr = new FontAttributes();
        InitializeComponent();
        InitList();
    }

    private void InitList()
    {
        ObservableCollection<Course> courses = new ObservableCollection<Course>();
        ListViewHistory.ItemsSource = courses;

        courses.Add(new Course() { Date = "1 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "2 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "3 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "4 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "5 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "6 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "7 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "8 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "9 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "10 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "11 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "12 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "13 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "14 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
        courses.Add(new Course() { Date = "15 Novembre 1995", Destination = "Le Mans", Price = "23.11" });
    }
}

and then its XAML MainPage.xaml.cs

<?xml version="1.0" encoding="utf-8" ?>
  <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         x:Class="Pages.CoursesHistory">
    <AbsoluteLayout>

      <ListView x:Name="ListViewHistory" BackgroundColor="White" RowHeight="50"
              AbsoluteLayout.LayoutBounds="0.5,0.5,1,1"
              AbsoluteLayout.LayoutFlags="All">
        <ListView.ItemTemplate>
          <DataTemplate>
            <ViewCell>

              <AbsoluteLayout>

The list is Bind with my ObservableCollection so how can I access FontAttr which is not bind?

                <Label FontFamily="{Binding Path=HOW_CAN_I_ACCESS_FONTATTR??}" 
                       Text="{Binding Date}" TextColor="Black" FontSize="14" VerticalTextAlignment="Center" HorizontalTextAlignment="Center"
                       AbsoluteLayout.LayoutBounds="0, 0.5, 0.3, 1"
                       AbsoluteLayout.LayoutFlags="All"/>
                <Label Text="{Binding Destination}" TextColor="Black" FontSize="14" VerticalTextAlignment="Center" HorizontalTextAlignment="Center"
                       AbsoluteLayout.LayoutBounds="0.5, 0.5, 0.5, 1"
                       AbsoluteLayout.LayoutFlags="All"/>
                <Label Text="{Binding Price}" TextColor="Black" FontSize="14" VerticalTextAlignment="Center" HorizontalTextAlignment="Center"
                       AbsoluteLayout.LayoutBounds="1, 0.5, 0.2, 1"
                       AbsoluteLayout.LayoutFlags="All"/>
              </AbsoluteLayout>

            </ViewCell>
          </DataTemplate>
        </ListView.ItemTemplate>
      </ListView>

    </AbsoluteLayout>
  </ContentPage>

Thank for read and for your help !

Answer 1

You need to use Relative Binding to achieve this.

First, you need to convert FontAttr to properties

public FontAttributes FontAttr { get; set; }

Then you need to set BindingContext to page itself as follows

public CoursesHistory()
{
    FontAttr = new FontAttributes();
    InitializeComponent();
    InitList();
    BindingContext=this;
}

Now you can use Relative Binding like this:

<ListView x:Name="ListViewHistory">
   <ListView.ItemTemplate>
      <DataTemplate>
        <ViewCell>
          <AbsoluteLayout>
              <Label FontFamily="{Binding Path=BindingContext.FontAttr.MOON_FAMILY_ALIEN_BOLD, Source={x:Reference Name=ListViewHistory}}" 
                   Text="{Binding Date}" TextColor="Black" FontSize="14" VerticalTextAlignment="Center" HorizontalTextAlignment="Center"
                   AbsoluteLayout.LayoutBounds="0, 0.5, 0.3, 1"
                   AbsoluteLayout.LayoutFlags="All"/>
            <Label Text="{Binding Destination}" TextColor="Black" FontSize="14" VerticalTextAlignment="Center" HorizontalTextAlignment="Center"
                   AbsoluteLayout.LayoutBounds="0.5, 0.5, 0.5, 1"
                   AbsoluteLayout.LayoutFlags="All"/>
            <Label Text="{Binding Price}" TextColor="Black" FontSize="14" VerticalTextAlignment="Center" HorizontalTextAlignment="Center"
                   AbsoluteLayout.LayoutBounds="1, 0.5, 0.2, 1"
                   AbsoluteLayout.LayoutFlags="All"/>
          </AbsoluteLayout>

        </ViewCell>
      </DataTemplate>
    </ListView.ItemTemplate>

Note I use Source={x:Reference Name=ListViewHistory} for relative binding.

Answer 2

In XAML, you should specify string format to display an double value.

<StackLayout Orientation="Horizontal">

    <Label x:Name="Name_Label_MeetingLocation1" 
        Text="{Binding Latitude , 
        StringFormat='{0:0.0000}'}"/>

</StackLayout>