How to set the BindableLayout.ItemsSource to an ObservableCollection in an other file

问题

Currently i have a TasksGroupPageViewModel.cs that contains my two ObservableCollection:

public ObservableCollection<TasksGroup> TasksGroups { get; set; } = new ObservableCollection<TasksGroup>();
public ObservableCollection<Tasks> Taches1 { get; set; } = new ObservableCollection<Tasks>();

The binding for my CollectionView which uses the TasksGroups data works, BUT i have a bindable stacklayout inside it but i am unable to bind it to his ObservableCollection data (taches1)

From the debuger i can see that it always try to access data from Models.TasksGroup.cs and not Models.Tasks.cs, it's like since my stacklayout is a children of the CollectionView, i can't bind to it

My question is : How can i directly bind to Taches1 ObservableCollection which is in TaskGroupPageViewModel with BindableLayout.ItemsSource="" or in .xaml.cs file but i didn't find a way to do it like i did for TasksGroup in the on appearing method

How i initialize my data in TaskGroupPage.xaml.cs (data1 is for TasksGroup and data2 is for Tasks :

 protected override async void OnAppearing()
   {
        base.OnAppearing();

        var data2 = await App.Database.GetAllTasks();
        var data1 = await App.Database.GetTaskGroupsAsync();

        var vm = this.BindingContext as TasksGroupPageViewModel;
        vm.TasksGroups = new ObservableCollection<TasksGroup>(data1);
        TasksGroupCollection.ItemsSource = vm.TasksGroups;
    
        vm.Taches1 = new ObservableCollection<Tasks>(data2);
}

How i bind to my collection view with x:Name=TasksGroupCollection

        <CollectionView Grid.Row="2" Margin="25" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand"
                SelectionMode="Single" x:Name="TasksGroupCollection" >

Inside this CollectionView i have a bindable stack layout which i want to bind to Taches1 data

                                      <StackLayout Grid.Column="2" Spacing="10" >
                                                <Label Text="Tâches" TextColor="Black" FontSize="15" Margin="20,0"/>
                                                <StackLayout BindableLayout.ItemsSource="{Binding }"  HorizontalOptions="Start" VerticalOptions="Center" Margin="20,0,0,20" x:Name="Taches1">
                                                    <BindableLayout.ItemTemplate >


                                                    <DataTemplate>
                                                            <Label TextColor="#2F3246" FontSize="12">
                                                                <Label.FormattedText>
                                                                    <FormattedString>
                                                                        <FormattedString.Spans>
                                                                            <Span Text="{Binding TaskDBA}"/>
                                                                            <Span Text=" - "/>
                                                                            <Span Text="{Binding TaskDescription}" FontAttributes="Bold"/>
                                                                        </FormattedString.Spans>
                                                                    </FormattedString>
                                                                </Label.FormattedText>
                                                            </Label>


                                                        </DataTemplate>
                                                        </BindableLayout.ItemTemplate >
                                                </StackLayout>

                                                
                                            </StackLayout>

回答1:

From the debuger i can see that it always try to access data from Models.TasksGroup.cs and not Models.Tasks.cs

When any element is included in a DataTemplate, the BindingContext will be the current item from the template's ItemsSource.

Your TasksGroupCollection.ItemsSource is vm.TasksGroups and there is no property called Taches1 in vm.TasksGroups, that's why you can't bind successfully.

Solution:

Taches1 is a property of vm and you should set the correct binding Source:

First, give a name to your ContentPage, let's say it MyPage:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"

             x:Name="MyPage"

             x:Class="App266.MainPage">

Then the bindingContext of your page is vm, bind the BindableLayout.ItemsSource to vm.Taches1 :

<StackLayout BindableLayout.ItemsSource="{Binding BindingContext.Taches1 , Source={x:Reference MyPage}}"  HorizontalOptions="Start" VerticalOptions="Center" Margin="20,0,0,20" x:Name="Taches1">

来源：https://stackoverflow.com/questions/62700725/how-to-set-the-bindablelayout-itemssource-to-an-observablecollection-in-an-other

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