feat: init avalonia demo.

src/Avalonia/HandyControlDemo_Avalonia/ViewModel/ViewModelLocator.cs

@@ -0,0 +1,26 @@
+using System;
+using HandyControlDemo.Service;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HandyControlDemo.ViewModel;
+
+public class ViewModelLocator
+{
+    private static readonly Lazy<ViewModelLocator> InstanceInternal = new(() => new ViewModelLocator(), isThreadSafe: true);
+
+    public static ViewModelLocator Instance => InstanceInternal.Value;
+
+    private readonly IServiceProvider _serviceProvider;
+
+    private ViewModelLocator()
+    {
+        var services = new ServiceCollection();
+
+        services.AddSingleton<DataService>();
+        services.AddTransient<MainViewModel>();
+
+        _serviceProvider = services.BuildServiceProvider();
+    }
+
+    public MainViewModel Main => _serviceProvider.GetService<MainViewModel>()!;
+}