{Binding .} doesn't work in release mode

[cat0363]

Description

If you use {Binding .} when a child references a view model that is bound to a parent, it will bind as intended in debug mode, but will not bind correctly in release mode. The reproduction code is shown below.

Below is the screen layout.

[MainPage.xaml]

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:Maui_IssueReleaseModeNotRendering"
             x:Class="Maui_IssueReleaseModeNotRendering.MainPage" x:DataType="local:ViewModelMainPage">

    <Grid BindingContext="{Binding EmployeeList}">
        <StackLayout Orientation="Vertical" Spacing="0" VerticalOptions="Start" BindableLayout.ItemsSource="{Binding .}">
            <BindableLayout.ItemTemplate>
                <DataTemplate x:DataType="local:ViewModelEmployee">
                    <Grid ColumnDefinitions="Auto,Auto,Auto" ColumnSpacing="5">
                        <Label Grid.Column="0" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeName}" />
                        <Label Grid.Column="1" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeAge}" />
                        <Label Grid.Column="2" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeSex}" />
                    </Grid>
                </DataTemplate>
            </BindableLayout.ItemTemplate>
        </StackLayout>
    </Grid>

</ContentPage>

Below is the view model used in the reproduction code.

[ViewModelMainPage.cs]

    public class ViewModelMainPage
    {
        public ObservableCollection<ViewModelEmployee> EmployeeList
        {
            get; set;
        }

        public ViewModelMainPage()
        {
            EmployeeList = new ObservableCollection<ViewModelEmployee>();
            EmployeeList.Add(new ViewModelEmployee() { EmployeeName = "Test1", EmployeeAge = 30, EmployeeSex = "Male" });
            EmployeeList.Add(new ViewModelEmployee() { EmployeeName = "Test2", EmployeeAge = 31, EmployeeSex = "Female" });
            EmployeeList.Add(new ViewModelEmployee() { EmployeeName = "Test3", EmployeeAge = 32, EmployeeSex = "Female" });
            EmployeeList.Add(new ViewModelEmployee() { EmployeeName = "Test4", EmployeeAge = 33, EmployeeSex = "Male" });
        }
    }

[ViewModelEmployee.cs]

    public class ViewModelEmployee
    {
        public string EmployeeName { get; set; }

        public int EmployeeAge { get; set; }

        public string EmployeeSex { get; set; }
    }

[MainPage.xaml.cs]

    public partial class MainPage : ContentPage
    {
        public ViewModelMainPage VmMainPage = new ViewModelMainPage();

        public MainPage()
        {
            InitializeComponent();

            BindingContext = VmMainPage;
        }
    }

Below is the result when running in debug mode.

[Debug mode]

Below is the result when running in release mode.

[Release mode]

If you build in release mode, {Binding .} is not working.

Is this way of writing not supported in release mode?

Steps to Reproduce

1. Build the app uploaded to GitHub in release mode and launch it on Android.

In step 1, nothing is displayed in the BindableLayout.

Link to public reproduction project repository

https://github.com/cat0363/Maui-IssueReleaseModeNotRendering.git

Version with bug

8.0.40 SR5

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

Android 11.0, 12.0, 13.0, 14.0

Did you find any workaround?

You can avoid this problem by explicitly specifying the view model without using {Binding .}.
For example, you can avoid this by doing the following:

    <Grid>
        <StackLayout Orientation="Vertical" Spacing="0" VerticalOptions="Start" BindableLayout.ItemsSource="{Binding EmployeeList}">
            <BindableLayout.ItemTemplate>
                <DataTemplate x:DataType="local:ViewModelEmployee">
                    <Grid ColumnDefinitions="Auto,Auto,Auto" ColumnSpacing="5">
                        <Label Grid.Column="0" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeName}" />
                        <Label Grid.Column="1" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeAge}" />
                        <Label Grid.Column="2" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeSex}" />
                    </Grid>
                </DataTemplate>
            </BindableLayout.ItemTemplate>
        </StackLayout>
    </Grid>

Relevant log output

No response

[github-actions]

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[cat0363]

Additional Information :
{Binding .} and {Binding} do not work.

[Zhanglirong-Winnie]

Verified this issue with Visual Studio 17.11.0 Preview 1.1 (8.0.40). Can repro on Android platform with sample project.

[simonrozsival]

@cat0363 there's a bug in your code. There's a mismatch between the x:DataType (ViewModelMainPage) and the binding context that's applied to {Binding .} (ObservableCollection<ViewModelEmployee>). The code in the "workaround" is correct.

Unfortunately, in Debug mode the values of x:DataType are ignored and so the non-compiled bindings will show the expected result. The following PR will make the experience the same across both configurations: #22056

Is this explanation enough? Can I go ahead and close this issue?

[cat0363]

@simonrozsival , Thank you for your explanation.
I didn't know that x:DataType was ignored in Debug mode.
Thanks for letting me know that PR #22056 makes the experience the same for both configurations.
I agree to close this issue.

As a side note, I got the expected results by doing the following.

[MainPage.xaml]

    <Grid BindingContext="{Binding EmployeeList}">
        <StackLayout Orientation="Vertical" Spacing="0" VerticalOptions="Start" x:DataType="local:EmployeeCollection" BindableLayout.ItemsSource="{Binding .}">
            <BindableLayout.ItemTemplate>
                <DataTemplate x:DataType="local:ViewModelEmployee">
                    <Grid ColumnDefinitions="Auto,Auto,Auto" ColumnSpacing="5">
                        <Label Grid.Column="0" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeName}" />
                        <Label Grid.Column="1" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeAge}" />
                        <Label Grid.Column="2" FontSize="14" TextColor="Black" VerticalOptions="Center" HorizontalOptions="Start" Text="{Binding EmployeeSex}" />
                    </Grid>
                </DataTemplate>
            </BindableLayout.ItemTemplate>
        </StackLayout>
    </Grid>

[MainPage.xaml.cs]

    public partial class MainPage : ContentPage
    {
        public ViewModelMainPage VmMainPage = new ViewModelMainPage();

        public MainPage()
        {
            InitializeComponent();

            BindingContext = VmMainPage;
        }
    }

[EmployeeCollection.cs]

    public class EmployeeCollection : ObservableCollection<ViewModelEmployee>;

[ViewModelMainPage.cs]

    public class ViewModelMainPage
    {
        public EmployeeCollection EmployeeList
        {
            get; set;
        }

        public ViewModelMainPage()
        {
            EmployeeList = new EmployeeCollection();
            EmployeeList.Add(new ViewModelEmployee() { EmployeeName = "Test1", EmployeeAge = 30, EmployeeSex = "Male" });
            EmployeeList.Add(new ViewModelEmployee() { EmployeeName = "Test2", EmployeeAge = 31, EmployeeSex = "Female" });
            EmployeeList.Add(new ViewModelEmployee() { EmployeeName = "Test3", EmployeeAge = 32, EmployeeSex = "Female" });
            EmployeeList.Add(new ViewModelEmployee() { EmployeeName = "Test4", EmployeeAge = 33, EmployeeSex = "Male" });
        }
    }

[ViewModelEmployee.cs]

    public class ViewModelEmployee
    {
        public string EmployeeName { get; set; }

        public int EmployeeAge { get; set; }

        public string EmployeeSex { get; set; }
    }