ViewLocator.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using Avalonia.Controls;
using Avalonia.Controls.Templates;
using NewRGB.ViewModels;

namespace NewRGB;

public class ViewLocator : IDataTemplate
{
    private static readonly Dictionary<Type, Func<Control>> Registration = new();

    public static void Register<TViewModel, TView>() where TView : Control, new()
    {
        Registration.Add(typeof(TViewModel), () => new TView());
    }

    public static void Register<TViewModel, TView>(Func<TView> factory) where TView : Control
    {
        Registration.Add(typeof(TViewModel), factory);
    }

    public Control Build(object? data)
    {
        Debug.Assert(data != null, nameof(data) + " != null");
        var type = data.GetType();

        return Registration.TryGetValue(type, out var factory)
            ? factory()
            : new TextBlock { Text = "Not Found: " + type };
    }

    public bool Match(object? data)
    {
        return data is ViewModelBase;
    }
}