Multiple data binding objects on a page

валера карманов 396

There is a code that goes to another page with the data binding specified

await Navigation.PushAsync(new HelpQuestionPage {
	BindingContext = e.CurrentSelection.FirstOrDefault()
});

In the class constructor I get the title to use as the page title

public HelpQuestionPage()
{
	SetBinding(TitleProperty, new Binding { Path = "title" });
}

This is all good, works like clockwork. HOWEVER. There is a function for the class "DataTemplate"

private Layout _GetDataTemplate()
{
	var field = new HelpQuestionRendererField();
	field.SetBindingLabel(Label.TextProperty, new Binding {
		Source = BindingContext, Path = "title"
	});
	var stackLayout = new VerticalStackLayout();
	field.RenderField(stackLayout);
	return stackLayout;
}

It uses the "BindingContext" data binding object, which is bound to the page itself, but I need the data binding that belongs to the "DataTemplate" class. How do I get it?

Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 32,386 Reputation points Microsoft Vendor

2024-10-08T03:22:32.4566667+00:00
but I need the data binding that belongs to the "DataTemplate" class.

Please try to set the Source to this.

field.SetBindingLabel(Label.TextProperty, new Binding { Source = this, Path = "title" });

From the code snippets, it's not clear what the e.CurrentSelection.FirstOrDefault() and TitleProperty are. If setting this doesn't work, please share more code snippets(whole page, viewmodel/Bindingcontext, DataTemplate class and so on) with me so that I can investigate further.

валера карманов 396

There is an abstract class "CollectionPage" that implements filling the "ItemsSource" property of the "CollectionView" element.

public abstract class CollectionPage : ContentPage
{
	protected CollectionView collection = new CollectionView();
	protected RefreshView refresh = new RefreshView();
	protected HttpRequest request = new HttpRequest();
	public CollectionPage()
	{
		collection.SelectionChanged += _OnSelectionChanged;
		collection.ItemTemplate = GetDataTemplate();
		LoadedCollection();
		refresh.Command = new Command(LoadedCollection);
		refresh.Content = collection;
		Content = refresh;
	}
	abstract protected DataTemplate GetDataTemplate();
	abstract protected void LoadedCollection();
	abstract protected Page GetContentPage(object? selected);
	async void _OnSelectionChanged(object? sender, SelectionChangedEventArgs e)
	{
		var selected = e.CurrentSelection.FirstOrDefault();
		await Navigation.PushAsync(GetContentPage(selected));
	}
}

This collection contains the "HelpGroup" classes.

public class HelpGroup
{
	public string id { get; set; } = "";
	public string title { get; set; } = "";
}

From the class it follows that the selected element will be passed to the function "GetContentPage" of the class "CollectionPage". In it I specify the data binding object as the selected class "HelpGroup".

The problem is in the class responsible for another page "GroupQuestionPage". It is called in the "_OnSelectionChanged" function of the "CollectionPage" class. When going to this page, the data binding object is already specified in it, so the code below works (it specifies the page title from the data binding object).

SetBinding(TitleProperty, new Binding { Path = "title" });

public class GroupQuestionPage : CollectionPage
{
	protected override void LoadedCollection()
	{
		request.loadedCollectionHelpQuestion(collection, refresh);
	}

	protected override DataTemplate GetDataTemplate()
	{
		return new DataTemplate(_GetDataTemplate);
	}

	public GroupQuestionPage() : base()
	{
		SetBinding(TitleProperty, new Binding { Path = "title" });
	}

	protected override Page GetContentPage(object? selected)
	{
		return new QuestionPage { BindingContext = selected };
	}

	private Layout _GetDataTemplate()
	{
		var field = new HelpQuestionRendererField();

		field.SetBindingLabel(Label.TextProperty, new Binding {
			Source = this, Path = "title"
		});

		var stackLayout = new VerticalStackLayout();
		field.RenderField(stackLayout);

		return stackLayout;
	}
}

According to the function in the code above, "GetDataTemplate" returns the class "DataTemplate" which contains the layout of the row element. In it, I need to get the data binding object of the class "HelpQuestion"

public class HelpQuestion
{
	public string id { get; set; } = "";
	public string title { get; set; } = "";
	public string introtext { get; set; } = "";
}

валера карманов 396 Reputation points

2024-10-08T06:27:32.86+00:00

123456
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 32,386 Reputation points Microsoft Vendor

2024-10-10T07:16:07.14+00:00

I tried to make a sample using the code snippets you provided, but I still confused about how you overwrite the DataTemplate method, and how you set the databinding. If it's possible, would you mind sharing a minimal reproducible sample with me? Please pay attention to protecting your private sensitive information.

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Multiple data binding objects on a page

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