Binding on Custom BindableProperty not working

Question

I'm having trouble binding values to a custom ContentView I have.

I have a ContentPage that uses a AccountStatusView that is a ContentView and has a BindableProperty. This BindableProperty is of type AccountStatus. When I try to use binding, the BindableProperty is never udpated.

Does someone know why this doesn't work?

MainPage - xaml

<Grid>
    <controls:AccountStatusView AccountStatus="{Binding AccountStatus}" />
</Grid>

MainPage - C#

public partial class MainPage : ContentPage
{
    public MainPage(ViewModel vm) {
        BindingContext = vm;
        InitializeComponent();
    }
}

ViewModel

public partial class ViewModel : ObservableObject
{
    [ObservableProperty] private AccountStatusDto _accountStatus;
    // . . .
    public async Task InitializeAsync()
    {
        AccountStatus = await _repo.GetAccountStatus();
    }
}

AccountStatusView

public partial class AccountStatusView : ContentView
{
    public static readonly BindableProperty AccountStatusProperty =
        BindableProperty.Create(nameof(AccountStatus), typeof(AccountStatusDto), typeof(AccountStatusView), propertyChanged: DoSomething);

    public static void DoSomething(BindableObject bindable, object oldvalue, object newvalue)
    {
        // do something with the new value
    }

    public AccountStatusDto AccountStatus
    {
        get => (AccountStatusDto)GetValue(AccountStatusProperty);
        set => SetValue(AccountStatusProperty, value);
    }

}

EDIT

I found this answer by ToolmakerSteve,

When making a custom component (that includes XAML), DO NOT set BindingContext = this;

And

ACCESS COMPONENT PROPERTIES VIA x:Name

Solution: Give the custom component (card) an x:Name, and make that the "Source" of those bindings:
    <VerticalStackLayout
        ...
        x:Name="me"     <-- IMPORTANT! Change name as desired.
        x:Class="DataBindingExample.Card">
        ...
        <Label Text="{Binding CardIncrement, Source={x:Reference me}}"
        ... 

And it worked perfectly

I checked the documentation and they have 'false' before callback in that example. Have you right everything? learn.microsoft.com/en-us/dotnet/maui/fundamentals/… — daremachine
– daremachine, Commented Sep 23, 2023 at 0:00
Yes, that false is the default value that you can give to the property. It's optional since the method signature assigns default to that parameter — Andres
– Andres, Commented Sep 23, 2023 at 0:06
If you want to set the BindingContext for a ContentView, you could set this.Content.BindingContext = new MyViewModel(); — Felix Shen
– Felix Shen, Commented Nov 1, 2023 at 6:42

Guangyu Bai - MSFT · Accepted Answer · 2023-09-25 03:30:36Z

0

I notice that you have found the solution, and I would like to add a few suggestions.

First, as ToolMakerSteve said that you can give the custom component (card) an x:Name, and make that the "Source" of those bindings:

  <VerticalStackLayout
        ...
        x:Name="me"     <-- IMPORTANT! Change name as desired.
        x:Class="DataBindingExample.Card">
        ...
        <Label Text="{Binding CardIncrement, Source={x:Reference me}}"
        ...

Second, you can also add the BindingContext to the same page in a control like the VerticalStackLayout. Then, you can bind the BindableProperty to the elements in the page.

<ContentView 
             ...
             x:Name="me">

    <VerticalStackLayout BindingContext="{x:Reference me}">
        <Entry x:Name="editAnswer" Text="{Binding  BindableProperty}"> 
    </VerticalStackLayout>
</ContentView>

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