.NET MAUI Community Toolkit Popup PopupHandler is incompatible

Question

I started working with .NET MAUI. I ran into a problem just by starting my development. I want to show a popup and I'm using the Community Toolkit.

All I did is:

I created a new .NET MAUI Application Project, installed the Community Toolkit NuGet Package (of course also the .UseMauiCommunityToolkit in the start up class) and added a XAML File for the Popup:

<?xml version="1.0" encoding="utf-8" ?>
<toolkit:Popup xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
               xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
               xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
               x:Class="TestApp.ProfilePopup">

    <VerticalStackLayout>
        <Label Text="This is a very important message!" />
    </VerticalStackLayout>

</toolkit:Popup>

I've no partial class for this popup

I just modified the button on MainPage to display the popup:

    private void OnCounterClicked(object sender, EventArgs e)
    {

        var popup = new ProfilePopup();

        this.ShowPopup(popup);

    }

If I run this application and click on the button to display the popup I'll get the error message:

CommunityToolkit.Maui.Core.Handlers.PopupHandler found for TestApp.ProfilePopup is incompatible

If I create the popup in C#, it works:

    private void OnCounterClicked(object sender, EventArgs e)
    {
        var popup = new Popup
        {
            Content = new VerticalStackLayout
            {
                Children =
        {
            new Label
            {
                Text = "This is a very important message!"
            }
        }
            }
        };

        this.ShowPopup(popup);

    }

Any idea what I'm doing wrong?

Thank you!

Markus

Answer 1

I reproduced the error message.

THE CAUSE: "I've no partial class for this popup".

That won't work. without that, there is no InitializeComponent call. The result is not a valid View.

---

To fix the problem,

First make sure you have got the toolkit registered in MauiProgram.cs:

using CommunityToolkit.Maui;
...

builder.UseMauiApp<App>().UseMauiCommunityToolkit();

then you must have

file ProfilePopup.xaml.cs containing:

public partial class ProfilePopup : CommunityToolkit.Maui.Views.Popup
{
    public ProfilePopup()
    {
        InitializeComponent();
    }
}

---

I generate custom views using these steps:

1. Project / Add New Item / .NET MAUI ContentView (XAML).
2. Give name "MyView". This adds TWO files to project: MyView.xaml and MyView.xaml.cs.
3. In MyView.xaml, add needed xmlns and change base class.
   Was:

<ContentView xmlns=...
    ...
    x:Class=...>
...
</ContentView>

change to:

<toolkit:Popup xmlns=
    ...
    xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
    x:Class=...>
...
</toolkit:Popup>

4. In MyView.xaml.cs, change base class.
   Was:

public partial class ProfilePopup : ContentView

change to:

public partial class ProfilePopup : CommunityToolkit.Maui.Views.Popup