<PackageReference Include="System.Windows.Extensions" Version="10.0.1" />

System.Xaml.Permissions.XamlAccessLevel

public class XamlAccessLevel
Defines access control to assemblies and types for purposes of XAML loading.
namespace System.Xaml.Permissions { public class XamlAccessLevel { public AssemblyName AssemblyAccessToAssemblyName { get; } public string PrivateAccessToTypeName { get; } public static XamlAccessLevel AssemblyAccessTo(Assembly assembly); public static XamlAccessLevel AssemblyAccessTo(AssemblyName assemblyName); public static XamlAccessLevel PrivateAccessTo(string assemblyQualifiedTypeName); public static XamlAccessLevel PrivateAccessTo(Type type); } }