Why isn't InitializeComponent available for the Application class?

[PlatinumLucario]

So I've got my test project as follows:

App.axaml:

<Application xmlns="https://github.com/avaloniaui"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
            xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
            xmlns:viewModels="clr-namespace:TestApplication"
            x:Class="TestApplication.App"
            Title="App"
            RequestedThemeVariant="Default">
   <Application.Styles>
      <FluentTheme />
   </Application.Styles>
</Application>

App.axaml.cs:

using System;
using System.Reflection;
using System.Threading;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Markup.Xaml;

[assembly: AssemblyTitle("TestApplication")]

namespace TestApplication;

public partial class App : Application {

   [STAThread]
   public static void Main(string[] args) {
      BuildAvaloniaApp().StartWithClassicDesktopLifetime(args);
      new App();
   }

   public App() {
      InitializeComponent();
   }

   private static AppBuilder BuildAvaloniaApp() {
      return AppBuilder.Configure<App>().UsePlatformDetect().LogToTrace();
   }

   public override void Initialize() {
      AvaloniaXamlLoader.Load(this);
   }
}

I really need to know, why isn't the InitializeComponent() isn't available for the Application class, despite it being available for the Window class and other classes when the axaml and axaml.cs are defined with the Application interface? It shows the following error:

error CS0103: The name 'InitializeComponent' does not exist in the current context

I even tried to ignore the error and tried building it, but it still fails with the same error

Because I need to port over a WPF project over to Avalonia, and the stuff that's previously available for WPF isn't available in Avalonia.

I tried looking everywhere for something similar, but no discussion has asked about the Application class specifically not working with InitializeComponent().

I really need to know why. Thank you.

[thevortexcloud]

You can use on OnFrameworkInitializationCompleted? You can also use the Initialize method, but that might be too early.

To be clear, Avalonia is not WPF. A lot things wont "just work" in Avalonia that work in WPF. For that you will need XPF. I also suggest reading some sample applications/docs.

[PlatinumLucario]

Yeah, makes sense. I was just seeing how much rewrites I'd need to make, and it looks like I'll need to rewrite huge amounts of the code in the project I'm contributing to in order to get every function working in Avalonia.

There's one sample that I used to actually get the splash screen working, so that was one workaround to one of the missing functions.

And XPF isn't an option, since XPF is a proprietary and paid product.

[thevortexcloud]

and it looks like I'll need to rewrite huge amounts of the code in the project I'm contributing to in order to get every function working in Avalonia.

In my experience, as long as there is not a huge amount of custom themeing going on/use of data triggers and the code is actually following MVVM properly, a lot of it is just find and replace. But the hard part is knowing what the equivalent feature is. I have ported some simple apps within ~10 minutes. More complicated ones can take anywhere from days to weeks.

[PlatinumLucario]

Unfortunately there is actually a lot of custom theming going on, and lots of property triggers in there, which is why I've opened a new discussion about it here: #19105