I have created a coupled Window <-> Controller (what I prefer to call my ViewModels) class relationship with the intent of handling a lot of boilerplate code that every window and controller uses.
Unfortunately though, this seems to have caused some form of runtime issue. I believe the problem is some form of bad pathing for my window’s DataContext, despite the fact I have no Bindings declared (yet) on the window…
public abstract class ModelledWindow<TWindow, TController> : Window
where TWindow : ModelledWindow<TWindow, TController>
where TController : WindowControllerBase<TWindow, TController>
{
protected TController Controller { get; }
public ModelledWindow(TController controller)
{
DataContext = Controller = controller ?? throw new ArgumentNullException(nameof(controller));
}
}
public abstract class ControllerBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected T Mutate<T>(T value, [CallerMemberName] string name = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
return value;
}
}
public abstract class WindowControllerBase<TWindow, TController> : ControllerBase
where TWindow : ModelledWindow<TWindow, TController>
where TController : WindowControllerBase<TWindow, TController>
{
public ICommand ShowWindowCmd { get; }
private Func<TWindow> WindowBuilder { get; }
public WindowControllerBase(CommandFactory commandFactory, Func<TWindow> windowBuilder)
{
ShowWindowCmd = commandFactory.Compose(ShowWindow, CanShowWindow);
WindowBuilder = windowBuilder ?? throw new ArgumentNullException(nameof(windowBuilder));
}
private TWindow _window;
private void ShowWindow()
{
_window ??= WindowBuilder();
_window.Show();
}
private Visibility Visibility => _window?.Visibility ?? Visibility.Hidden;
private bool CanShowWindow() => Visibility != Visibility.Visible;
}
MainWindow.xaml:
<local:ModelledWindow
x:Class="PoeAutoClipboard.Wpf.MainWindow"
x:TypeArguments="local:MainWindow,local:MainWindowController"
xmlns:local="clr-namespace:PoeAutoClipboard.Wpf"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Title="PoeAutoClipboard"
Height="46"
Width="155"
>
<Grid>
</Grid>
</local:ModelledWindow>
MainWindow.xaml.cs:
public partial class MainWindow : ModelledWindow<MainWindow, MainWindowController>
{
public MainWindow(MainWindowController controller) : base(controller)
{
InitializeComponent();
}
}
public class MainWindowController : WindowControllerBase<MainWindow, MainWindowController>
{
public MainWindowController(
CommandFactory commandFactory,
Func<MainWindow> windowBuilder
) : base(commandFactory, windowBuilder)
{
}
}
I automatically scaffold everything up via Dependency Injection in my App layer like so:
public partial class App : Application
{
private const string ConfigurationPath = "AppSettings.json";
private ConfigurationController ConfigController { get; set; }
public App()
{
var config = new ConfigurationBuilder()
.AddJsonFile(ConfigurationPath, true, true)
.Build();
ConfigController = config.Get<ConfigurationController>() ?? new ConfigurationController();
}
private void App_OnStartup(object sender, StartupEventArgs e)
{
var services = new ServiceCollection();
ConfigureServices(services);
var serviceProvider = services.BuildServiceProvider();
var mainWindow = serviceProvider.GetRequiredService<MainWindowController>();
mainWindow.ShowWindowCmd.Execute(null);
}
private void ConfigureServices(IServiceCollection services)
{
services.UseMVC<App>();
// Remove the auto registered "blank" config and add our loaded config VM instead
services.Remove(ServiceDescriptor.Singleton(typeof(ConfigurationController)));
services.AddSingleton(ConfigController);
// Services
services.AddSingleton<CommandFactory>();
}
}
When I inspect MainWindowController and MainWindow everything seems fine. The Controller is not null and the DataContext has been assigned the way I expected it to be. I can inspect MainWindow.DataContext and its as I expect to be (a non-null instance of MainWindowController)
Furthermore, MainWindow.gics appears to be working exactly as expected, its building as such:
public partial class MainWindow : PoeAutoClipboard.Wpf.ModelledWindow<PoeAutoClipboard.Wpf.MainWindow, PoeAutoClipboard.Wpf.MainWindowController>, System.Windows.Markup.IComponentConnector {
...
}
Everything compiles and runs fine, but then I hit a runtime exception here, in the Constructor of MainWindow:
private void App_OnStartup(object sender, StartupEventArgs e)
{
var services = new ServiceCollection();
ConfigureServices(services);
var serviceProvider = services.BuildServiceProvider();
var mainWindow = serviceProvider.GetRequiredService<MainWindowController>();
mainWindow.ShowWindowCmd.Execute(null); <<<<<< Here (Calling method up stack)
}
public MainWindow(MainWindowController controller) : base(controller)
{
InitializeComponent(); <<<<<< Here (Actual exception thrown here)
}
And the exception is… extremely unhelpful.
Message: System.NullReferenceException: ‘Object reference not set to an instance of an object.’
Stack Trace:
at System.Windows.Markup.WpfXamlLoader.TransformNodes(XamlReader xamlReader, XamlObjectWriter xamlWriter, Boolean onlyLoadOneNode, Boolean skipJournaledProperties, Boolean shouldPassLineNumberInfo, IXamlLineInfo xamlLineInfo, IXamlLineInfoConsumer xamlLineInfoConsumer, XamlContextStack`1 stack, IStyleConnector styleConnector)
at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
at PoeAutoClipboard.Wpf.MainWindow.InitializeComponent() in D:DocumentsProjectsProgrammingCSharpPoeAutoClipboardPoeAutoClipboard.WpfMainWindow.xaml:line 1
at PoeAutoClipboard.Wpf.MainWindow..ctor(MainWindowController controller) in D:DocumentsProjectsProgrammingCSharpPoeAutoClipboardPoeAutoClipboard.WpfMainWindow.xaml.cs:line 14
at System.RuntimeMethodHandle.InvokeMethod(Object target, Span`1& arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitDisposeCache(ServiceCallSite transientCallSite, RuntimeResolverContext context)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass2_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
at PoeAutoClipboard.Wpf.WindowControllerBase`2.ShowWindow() in D:DocumentsProjectsProgrammingCSharpPoeAutoClipboardPoeAutoClipboard.WpfControllerBase.cs:line 34
at PoeAutoClipboard.Wpf.Extensions.CommandFactoryExtensions.<>c__DisplayClass4_0.<Compose>b__0(Object p) in D:DocumentsProjectsProgrammingCSharpPoeAutoClipboardPoeAutoClipboard.WpfExtensionsCommandFactoryExtensions.cs:line 33
at PoeAutoClipboard.Wpf.Command.Execute(Object parameter) in D:DocumentsProjectsProgrammingCSharpPoeAutoClipboardPoeAutoClipboard.WpfCommand.cs:line 23
at PoeAutoClipboard.Wpf.App.App_OnStartup(Object sender, StartupEventArgs e) in D:DocumentsProjectsProgrammingCSharpPoeAutoClipboardPoeAutoClipboard.WpfApp.xaml.cs:line 38
at System.Windows.Application.OnStartup(StartupEventArgs e)
at System.Windows.Application.<.ctor>b__1_0(Object unused)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state)
at MS.Internal.CulturePreservingExecutionContext.CallbackWrapper(Object obj)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
No Inner Exception.
Anyone have insight on what I missed here? Also, if I change my code in App Startup to this, it throws the exact same exception:
private void App_OnStartup(object sender, StartupEventArgs e)
{
var services = new ServiceCollection();
ConfigureServices(services);
var serviceProvider = services.BuildServiceProvider();
var mainWindow = serviceProvider.GetRequiredService<MainWindow>();
mainWindow.Show(); <<<<<< Breaks here, same exception, throws on same spot in MainWindow Constructor
}