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Display a ToolBar in a Xamarin.Forms modal page

The "new" and recommended way to display a modal page with the Xamarin.Forms Shell uri-based navigation is to set this tag in the XAML file (source): Shell.PresentationMode="ModalAnimated"
and to navigate to it by using a standard route and invoking it with the function Shell.Current.GoToAsync("routeToMyPage").
However, this displays the modal page without a toolbar. Without Shell navigation, I would have wrapped this page in a NavigationPage, but since the pages are initialized through reflection (at least that's what it looks like - don't quote me on this), I don't know how to do that.
Adding a ToolbarItem in the page's XAML code doesn't solve this, neither does the Shell.NavBarIsVisible="True" property, and adding a Button in the Shell.TitleView tag doesn't display a toolbar either.
Is there a way to display the default navigation toolbar without rendering a custom one myself?
Here is the XAML code I used to try to have the Toolbar displayed:
<ContentPage
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
Shell.PresentationMode="ModalAnimated"
Shell.NavBarIsVisible="True"
x:Class="StackOverflow.Views.MyModalPage">
<ContentPage.ToolbarItems >
<ToolbarItem Text="Hi"/>
</ContentPage.ToolbarItems>
<Shell.TitleView>
<Button Text="Toolbar Button"/>
</Shell.TitleView>
<ContentPage.Content>
</ContentPage.Content>
</ContentPage>
Edit: I have created a small sample project to showcase my issue: https://github.com/Kuurse/StackOverflowExample

You can first create the NavigationPage root page in the app class:
public partial class App : Application
{
public App()
{
InitializeComponent();
MainPage = new NavigationPage(new MainPage());
}
}
Then set like this in your mainpage.xaml:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="StackOverflow.Views.MyModalPage"
NavigationPage.HasNavigationBar="True">
<ContentPage.ToolbarItems>
<ToolbarItem Text="Hi"/>
</ContentPage.ToolbarItems>
</ContentPage>
By the way, do you want to display only the default navigation toolbar?

How to set size of Xamarin Community Toolkit Popup to wrap content dynamically in Xamarin Forms?

I have a Xamarin.CommunityToolkit - Popup. I don't want to predefine its size. I want it to size according to the content dynamically. Is there any way to achieve this?
Here is my XAML code:
<?xml version="1.0" encoding="UTF-8"?>
<xct:Popup xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
x:Class="SampleProject.Views.SamplePopup">
<StackLayout>
<Label Text="Hello Xamarin.Forms!" />
<Button Text="Close Popup" Clicked="ClosePopup" />
</StackLayout>
</xct:Popup>

The current implementation doesn't support such feature, as Amjad mentioned in his comment there was a similar feature request in the past but it was closed as things were migrating to the new repo .NET MAUI community toolkit.
If you are interested you can open a discussion explaining or pointing to the link of that feature request.

Setting my partial View, not working xamarin

Now I got started with Prism Framework for xamarine, but I'm having a little problem achieving connections across views.
I have this folder "Views" and inside it I have another folder called PartialViews. Now inside PartialViews I have a contentPage called "Header.xaml".
Now I would like to atach this file to the Index.xaml view, which is located in the Views folder. I would like to atach the "Header.xaml" to other views also, like for example I would like to atach it to the "Orders.xaml" view.
My Header.xaml file is as follows :
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:prism="http://prismlibrary.com"
xmlns:local="clr-namespace:PROJECTX.Views"
prism:ViewModelLocator.AutowireViewModel="True"
x:Class="PROJECTX.Views.Header">
<StackLayout>
<Label Text="Trying partial views" />
</StackLayout>
</ContentPage>
While my Index.xaml is as follows:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:combobox="clr-namespace:Syncfusion.XForms.ComboBox;assembly=Syncfusion.SfComboBox.XForms"
xmlns:ListCollection="clr-namespace:System.Collections.Generic;assembly=mscorlib"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:prism="http://prismlibrary.com"
xmlns:local="clr-namespace:PROJECTX.Views"
prism:ViewModelLocator.AutowireViewModel="True"
x:Class="PROJECTX.Views.Index"
x:Name="selfi">
<ScrollView>
<local:Header mvvm:ViewModelLocator.AutowirePartialView="{x:Reference selfi}" />
<combobox:SfComboBox x:Name="comboBox">
<combobox:SfComboBox.ComboBoxSource>
<ListCollection:List x:TypeArguments="x:String">
<x:String>Rendit sipas: Me te kerkuara</x:String>
<x:String>Rendit sipas: Te fundit</x:String>
<x:String>Rendit sipas: Alfabetit</x:String>
</ListCollection:List>
</combobox:SfComboBox.ComboBoxSource>
</combobox:SfComboBox>
</ScrollView>
</ContentPage>
I also registred on my App.xaml.cs the routing of the PartialViews folder with the view model like this:
protected override void RegisterTypes(IContainerRegistry containerRegistry)
{
containerRegistry.RegisterForNavigation<NavigationPage>();
containerRegistry.RegisterForNavigation<MainPage, MainPageViewModel>();
containerRegistry.RegisterForNavigation<Index, IndexViewModel>();
//containerRegistry.RegisterForNavigation<Header, HeaderViewModel>();
ViewModelLocationProvider.Register<Header, HeaderViewModel>();
}
Now I get a few errors...
1. The property 'Content' is set more than once.
2. The attachable property 'AutowirePartialView' was not found in type 'ViewModelLocator'.
3. Property 'Content' does not support values of type 'Header'.
Now I know this might be a rookie question, but I just can't seem to get it to work this partial views thing.
Is my understanding of partial views in xamarin correct? I'm supposed to call the partial view from the view.. correct?
Any help I would really really appreciate.

So you have to understand that in Xamarin forms, you can only have one ContentPage object for a page, hence you are getting the error “Content is set more than once”. You can however have multiple Layouts inside a single page
Here’s a quick snippet explaining pages versus layouts
Since you’re looking to use the Prism "PartialViews", a common way of referencing them is a "Template". So you’d have a HeaderTemplate file as you have shared. But instead of a ContentPage object, you would use a ContentView object (which is of type Layout) and you would define the content of the header inside that. (Official Docs)
And then you can add it to any page using this line inside your XAML as you would add a regular layout:
<templates: HeaderTemplate/>

C# to Xaml Conversion

I want to implement a custom accordion ui element but the code has been written in C# ( https://github.com/Kimserey/AccordionView ) but I want to use xaml. I tried to add Accordion view in my content but while I am compiling I get following error
HomePage.xaml : error : The given key was not present in the dictionary.
Here is the my xaml code
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:customaccordionmenu="clr-namespace:CustomAccordionMenu"
x:Class="CustomAccordionMenu.HomePage" Title="Accordion Example" >
<ContentPage.Content>
<StackLayout VerticalOptions = "Center">
<customaccordionmenu:AccordionView/>
</StackLayout>
</ContentPage.Content>
</ContentPage>
So I just want to create an accordionview and add the content in xaml, not in c#
PS: The project is for Xamarin.Forms

You are trying to instantiate an empty AccordionView. Judging by the code in github, the accordionview doesn't have a parameterless constructor, which could cause a problem.
Also the AccordionSectionView class calls
private ImageSource _arrowRight = ImageSource.FromFile("ic_keyboard_arrow_right_white_24dp.png");
as well as
private ImageSource _arrowDown = ImageSource.FromFile("ic_keyboard_arrow_down_white_24dp.png");
so if these files aren't in your app's resources and named in the very same way, this is also a possible cause for a crash.

Problems to create custom attributes xmlns:android="schemas.android" Xamarin Studio

I'm new in Xamarin Studio, I'm trying to create a custom attribute in XAML, in a cross plataform solution, I´m using the xmlns:android="http://schemas.android.com/apk/res/android" reference, but when I use the prefix android:text="Hello world", and I run the solution it show me an error of "property 'text' was not found" at this line of code.
XAML Code:
<ContentPage.Content>
<Label Text="Hellow Word"
android:textStyle="Italic"> </Label>
</ContentPage.Content > </ContentPage>
Manifest Code:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
android:versionCode="1"
android:versionName="1.0"
package="app.monodroid">
<uses-sdk android:minSdkVersion="15" />
<application android:label="Push_Money_N">
</application>
</manifest>
Error:
Thanks for any help, I have been trying for many days to solve this problem. I'm very new to Xamarin Studio, and I've worked with Android Studio before and in it I can use this custom attribute. Thanks.