Databinding in XAML for MasterDetailPage in Xamarin.Forms

Question

So far, most examples using Xamarin.Forms are using C# for building up the UI. I prefer using XAML for the UI, and databind it to ViewModels.

I'm having trouble using the Xamarin.Forms.MasterDetailPage in combination with XAML, and I can't seem to port the C# example to XAML + ViewModels.

This is the XAML I got so far:

<?xml version="1.0" encoding="UTF-8" ?> 
<MasterDetailPage
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:local="clr-namespace:NSContacten;assembly=NSContacten"
    x:Class="MasterDetailExample.Main"
    Title="Master Detail Example">

    <MasterDetailPage.Master BindingContext="{Binding Menu}">
        <ContentPage Padding="5, 25">               
            <StackLayout Orientation="Vertical">
                <Label Text="Master" HorizontalOptions="Center" />
                <Label Text="{Binding Subtitle}" HorizontalOptions="Center" />
            </StackLayout>    
        </ContentPage>
    </MasterDetailPage.Master>

    <MasterDetailPage.Detail BindingContext="{Binding Detailpage}">
        <ContentPage Padding="5, 25">    
            <StackLayout Orientation="Vertical">
                <Label Text="Detail" HorizontalOptions="Center" />
                <Label Text="{Binding Subtitle}" HorizontalOptions="Center" />
            </StackLayout>    
        </ContentPage>
    </MasterDetailPage.Detail>    
</MasterDetailPage>

The component works: I do see the 'Master' and 'Detail' labels. The bound labels (on the BindingContext objects) are not displayed.

I've used loads of different combinations, but I'm still stuck: How does this work? Is my binding incorrect (should it be on the "ContentPage"), can't I bind to the .Master and .Detail properties etc.? How should the "Menu" and "Detailpage" bindings look like?

It would be a huge help if anyone could help me out! The next step would be that the .Detail will be changed when a button is pressed in the .Master . Thanks in advance!

Answer 1

Your Xaml is almost ok, but:

• The {BindingContext} are invalid on the properties and should be on the ContentPage elements
• MasterDetailPage.Master require a Page.Title to be set, or it throws.

Here's the correct Xaml working for me:

<?xml version="1.0" encoding="UTF-8" ?> 
<MasterDetailPage
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:local="clr-namespace:NSContacten;assembly=NSContacten"
    x:Class="MasterDetailExample.Main"
    Title="Master Detail Example">

    <MasterDetailPage.Master>
      <ContentPage Padding="5, 25"  BindingContext="{Binding Menu}" Title="Master">
          <StackLayout Orientation="Vertical">
              <Label Text="Master" HorizontalOptions="Center" />
              <Label Text="{Binding Subtitle}" HorizontalOptions="Center" />
          </StackLayout>
        </ContentPage>

    </MasterDetailPage.Master>

    <MasterDetailPage.Detail>
        <ContentPage Padding="5, 25"  BindingContext="{Binding Detailpage}">

          <StackLayout Orientation="Vertical">
              <Label Text="Detail" HorizontalOptions="Center" />
              <Label Text="{Binding Subtitle}" HorizontalOptions="Center" />
          </StackLayout>

        </ContentPage>
    </MasterDetailPage.Detail>
</MasterDetailPage>

I tested it with an anonymous type as the page view model:

public MyMDPage ()
{
    InitializeComponent ();
    BindingContext = new {
        Menu = new { Subtitle = "I'm Master" },
        Detailpage = new { Subtitle = "I'm Detail" }
    };
}

and this works just fine. In your case, you probably want concrete types instead of anonymous ones for your view model, but you get the idea.