PresenceApp/Presence.Desktop/ViewLocator.cs

using Avalonia.Controls;
using Avalonia.Controls.Templates;
using Presence.Desktop.ViewModels;
using System;
using Presence.Desktop.Views;
using ReactiveUI;

namespace Presence.Desktop
{
    public class ViewLocator : IViewLocator
    {
        public IViewFor? ResolveView<T>(T? viewModel, string? contract = null) => viewModel switch
        {
            GroupViewModel groupViewModel => new GroupView{DataContext = groupViewModel},
            PresenceViewModel presenceViewModel => new PresenceView{DataContext = presenceViewModel},
            _ => throw new ArgumentOutOfRangeException(nameof(viewModel))
        };
    }
}