PrismでViewとViewModelを別アセンブリにする場合のコードサンプル

Bootstrapper.cs

        ViewTypeToViewModelTypeResolver _resolver;
        protected override void ConfigureViewModelLocator()
        {
            base.ConfigureViewModelLocator();
            _resolver = new ViewTypeToViewModelTypeResolver(typeof(MainWindowViewModel).Assembly); // とりあえず適当なVMからAssembly取得して設定しておく
            ViewModelLocationProvider.SetDefaultViewTypeToViewModelTypeResolver(_resolver.Resolve);
        }

        public class ViewTypeToViewModelTypeResolver
        {
            private readonly Assembly _assembly;

            public ViewTypeToViewModelTypeResolver(Assembly assembly)
            {
                _assembly = assembly;
            }

            public Type Resolve(Type viewType)
            {
                if (viewType == null) throw new ArgumentNullException(nameof(viewType));

                // ReSharper disable once PossibleNullReferenceException
                var vmTypeName = $"{viewType.Namespace.Replace("Views", "ViewModels")}.{viewType.Name}ViewModel";
                var vmType = _assembly.GetType(vmTypeName);
                return vmType;
            }
        }