Windows navigation

Question

in .net 9, we have a new control named Window.TitleBar, so now we can play with some pages on Mobile and windows on Desktop

I created

Page1

Window1

I register them both

  public partial class AppShell : Shell {
      public AppShell() {
          InitializeComponent();
          Routing.RegisterRoute(nameof(Window1), typeof(Window1));
          Routing.RegisterRoute(nameof(Page1), typeof(Page1));
      }

and created an implementation of an interface, that will help me navigate

   public async Task NavigateTo(string baseRoute, bool animated = true) {

       // Generate the dynamic route based on the platform
       string route = baseRoute;

       // If the device is Desktop (Windows), append "Windows" to the base route (e.g., "Page1" becomes "Windows1")
       if (DeviceInfo.Idiom == DeviceIdiom.Desktop) {
           route = $"Window{baseRoute.Substring(4)}";  // Assuming the base route starts with "Page" (e.g., "Page1" => "Windows1")
       }

       /
       

       // Now navigate to the dynamically generated route
       await Shell.Current.GoToAsync(route, animated);
   }

For mobile is navigation fne

but for wndows I get

-		$exception	{"Object reference not set to an instance of an object."}	System.NullReferenceException
+		Data	Count = 0	System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
		HResult	-2147467261	int
		HasBeenThrown	true	bool
		HelpLink	null	string
+		InnerException	null	System.Exception
		Message	"Object reference not set to an instance of an object."	string
		SerializationStackTraceString	"   at Microsoft.Maui.Controls.ShellNavigationManager.ApplyQueryAttributes(Element element, ShellRouteParameters query, Boolean isLastItem, Boolean isPopping)"	string
		SerializationWatsonBuckets	null	object
		Source	"Microsoft.Maui.Controls"	string
		StackTrace	"   at Microsoft.Maui.Controls.ShellNavigationManager.ApplyQueryAttributes(Element element, ShellRouteParameters query, Boolean isLastItem, Boolean isPopping)"	string
+		TargetSite	{Void ApplyQueryAttributes(Microsoft.Maui.Controls.Element, Microsoft.Maui.Controls.ShellRouteParameters, Boolean, Boolean)}	System.Reflection.MethodBase {System.Reflection.RuntimeMethodInfo}
		_HResult	-2147467261	int
+		_data	Count = 0	System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
		_exceptionMethod	null	System.Reflection.MethodBase
		_helpURL	null	string
+		_innerException	null	System.Exception
		_ipForWatsonBuckets	0x00007fff0730abbf	System.UIntPtr
		_message	"Object reference not set to an instance of an object."	string
		_remoteStackTraceString	null	string
		_source	null	string
+		_stackTrace	{sbyte[48]}	object {sbyte[]}
		_stackTraceString	null	string
		_watsonBuckets	null	byte[]
		_xcode	-532462766	int
		_xptrs	0x0000000000000000	System.IntPtr
+		Static members		

here is the viewModel

public partial class MainPageViewModel(IAppService appService) : ObservableObject {

    [RelayCommand]
    async Task nav() {

        string route = "Page1"; // This can be dynamically determined based on some conditions if needed

        // Call the AppService to perform the navigation (platform-specific logic happens inside AppServices)
        await appService.NavigateTo(route);
    }

Answer 1

Hello,

If you want to open the window, you cannot use Shell.Current.GoToAsync to navigate to the window.

You can use Application.Current?.OpenWindow(new Window1()); to open it.

You can refer to this document: Multi-window support

You can set the Page1 to page property in the NewWindow1. You do not need to Routing.RegisterRoute(nameof(Window1), typeof(Window1)); in the AppShell.

public partial class NewWindow1 : Window
{
	public NewWindow1()
	{
		InitializeComponent();
		Page = new Page1();
	}
}

By the way, if you just want to open the window for windows platform.

You can use conditional compilation to do it.

#if WINDOWS

            Application.Current?.OpenWindow(new Window1());
 
#endif

Best Regards,

Leon Lu

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