Adding TryRegister

src/Forms/Prism.Forms/PrismApplicationBase.cs

@@ -168,18 +168,18 @@ protected virtual void Initialize()
         /// <param name="containerRegistry"></param>
         protected virtual void RegisterRequiredTypes(IContainerRegistry containerRegistry)
         {
-            containerRegistry.RegisterSingleton<IApplicationProvider, ApplicationProvider>();
-            containerRegistry.RegisterSingleton<IApplicationStore, ApplicationStore>();
-            containerRegistry.RegisterSingleton<IEventAggregator, EventAggregator>();
-            containerRegistry.RegisterSingleton<IKeyboardMapper, KeyboardMapper>();
-            containerRegistry.RegisterSingleton<IPageDialogService, PageDialogService>();
-            containerRegistry.RegisterSingleton<IDialogService, DialogService>();
-            containerRegistry.RegisterSingleton<IDeviceService, DeviceService>();
-            containerRegistry.RegisterSingleton<IPageBehaviorFactory, PageBehaviorFactory>();
-            containerRegistry.RegisterSingleton<IModuleCatalog, ModuleCatalog>();
-            containerRegistry.RegisterSingleton<IModuleManager, ModuleManager>();
-            containerRegistry.RegisterSingleton<IModuleInitializer, ModuleInitializer>();
-            containerRegistry.RegisterScoped<INavigationService, PageNavigationService>();
+            containerRegistry.TryRegisterSingleton<IApplicationProvider, ApplicationProvider>();
+            containerRegistry.TryRegisterSingleton<IApplicationStore, ApplicationStore>();
+            containerRegistry.TryRegisterSingleton<IEventAggregator, EventAggregator>();
+            containerRegistry.TryRegisterSingleton<IKeyboardMapper, KeyboardMapper>();
+            containerRegistry.TryRegisterSingleton<IPageDialogService, PageDialogService>();
+            containerRegistry.TryRegisterSingleton<IDialogService, DialogService>();
+            containerRegistry.TryRegisterSingleton<IDeviceService, DeviceService>();
+            containerRegistry.TryRegisterSingleton<IPageBehaviorFactory, PageBehaviorFactory>();
+            containerRegistry.TryRegisterSingleton<IModuleCatalog, ModuleCatalog>();
+            containerRegistry.TryRegisterSingleton<IModuleManager, ModuleManager>();
+            containerRegistry.TryRegisterSingleton<IModuleInitializer, ModuleInitializer>();
+            containerRegistry.TryRegisterScoped<INavigationService, PageNavigationService>();
             containerRegistry.Register<INavigationService, PageNavigationService>(NavigationServiceName);
         }
 

src/Maui/Prism.Maui/Ioc/RegionNavigationRegistrationExtensions.cs

@@ -98,7 +98,7 @@ private static IServiceCollection RegisterForNavigationWithViewModel(this IServi
 
     internal static IContainerRegistry RegisterRegionServices(this IContainerRegistry containerRegistry, Action<RegionAdapterMappings> configureAdapters = null, Action<IRegionBehaviorFactory> configureBehaviors = null)
     {
-        containerRegistry.Register<IRegionNavigationRegistry, RegionNavigationRegistry>();
+        containerRegistry.TryRegister<IRegionNavigationRegistry, RegionNavigationRegistry>();
         containerRegistry.RegisterSingleton<RegionAdapterMappings>(p =>
         {
             var regionAdapterMappings = new RegionAdapterMappings();
@@ -114,10 +114,10 @@ internal static IContainerRegistry RegisterRegionServices(this IContainerRegistr
             return regionAdapterMappings;
         });
 
-        containerRegistry.RegisterSingleton<IRegionManager, RegionManager>();
-        containerRegistry.RegisterSingleton<IRegionNavigationContentLoader, RegionNavigationContentLoader>();
-        containerRegistry.RegisterSingleton<IRegionViewRegistry, RegionViewRegistry>();
-        containerRegistry.Register<RegionBehaviorFactory>();
+        containerRegistry.TryRegisterSingleton<IRegionManager, RegionManager>();
+        containerRegistry.TryRegisterSingleton<IRegionNavigationContentLoader, RegionNavigationContentLoader>();
+        containerRegistry.TryRegisterSingleton<IRegionViewRegistry, RegionViewRegistry>();
+        containerRegistry.TryRegister<RegionBehaviorFactory>();
         containerRegistry.RegisterSingleton<IRegionBehaviorFactory>(p =>
         {
             var regionBehaviors = p.Resolve<RegionBehaviorFactory>();
@@ -132,10 +132,10 @@ internal static IContainerRegistry RegisterRegionServices(this IContainerRegistr
             configureBehaviors?.Invoke(regionBehaviors);
             return regionBehaviors;
         });
-        containerRegistry.Register<IRegionNavigationJournalEntry, RegionNavigationJournalEntry>();
-        containerRegistry.Register<IRegionNavigationJournal, RegionNavigationJournal>();
-        containerRegistry.Register<IRegionNavigationService, RegionNavigationService>();
+        containerRegistry.TryRegister<IRegionNavigationJournalEntry, RegionNavigationJournalEntry>();
+        containerRegistry.TryRegister<IRegionNavigationJournal, RegionNavigationJournal>();
+        containerRegistry.TryRegister<IRegionNavigationService, RegionNavigationService>();
         //containerRegistry.RegisterManySingleton<RegionResolverOverrides>(typeof(IResolverOverridesHelper), typeof(IActiveRegionHelper));
-        return containerRegistry.RegisterSingleton<IRegionManager, RegionManager>();
+        return containerRegistry.TryRegisterSingleton<IRegionManager, RegionManager>();
     }
 }

src/Maui/Prism.Maui/PrismAppBuilder.cs

@@ -220,16 +220,16 @@ public PrismAppBuilder ConfigureRegionBehaviors(Action<IRegionBehaviorFactory> c
 
     private void RegisterDefaultRequiredTypes(IContainerRegistry containerRegistry)
     {
-        containerRegistry.RegisterSingleton<IEventAggregator, EventAggregator>();
-        containerRegistry.RegisterSingleton<IKeyboardMapper, KeyboardMapper>();
-        containerRegistry.RegisterScoped<IPageDialogService, PageDialogService>();
-        containerRegistry.RegisterScoped<IDialogService, DialogService>();
-        containerRegistry.Register<IDialogViewRegistry, DialogViewRegistry>();
+        containerRegistry.TryRegisterSingleton<IEventAggregator, EventAggregator>();
+        containerRegistry.TryRegisterSingleton<IKeyboardMapper, KeyboardMapper>();
+        containerRegistry.TryRegisterScoped<IPageDialogService, PageDialogService>();
+        containerRegistry.TryRegisterScoped<IDialogService, DialogService>();
+        containerRegistry.TryRegister<IDialogViewRegistry, DialogViewRegistry>();
         containerRegistry.RegisterDialogContainer<DialogContainerPage>();
         //containerRegistry.RegisterSingleton<IDeviceService, DeviceService>();
-        containerRegistry.RegisterScoped<IPageAccessor, PageAccessor>();
-        containerRegistry.RegisterScoped<INavigationService, PageNavigationService>();
-        containerRegistry.Register<INavigationRegistry, NavigationRegistry>();
+        containerRegistry.TryRegisterScoped<IPageAccessor, PageAccessor>();
+        containerRegistry.TryRegisterScoped<INavigationService, PageNavigationService>();
+        containerRegistry.TryRegister<INavigationRegistry, NavigationRegistry>();
         containerRegistry.RegisterManySingleton<PrismWindowManager>();
         containerRegistry.RegisterPageBehavior<NavigationPage, NavigationPageSystemGoBackBehavior>();
         containerRegistry.RegisterPageBehavior<NavigationPage, NavigationPageActiveAwareBehavior>();

src/Prism.Core/Ioc/IContainerRegistryExtensions.cs

@@ -7,6 +7,141 @@ namespace Prism.Ioc
     /// </summary>
     public static class IContainerRegistryExtensions
     {
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <param name="from">The service type.</param>
+        /// <param name="to">The implementation type.</param>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegister(this IContainerRegistry containerRegistry, Type from, Type to)
+        {
+            if (!containerRegistry.IsRegistered(from))
+                containerRegistry.Register(from, to);
+
+            return containerRegistry;
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <typeparam name="TFrom">The service type.</typeparam>
+        /// <typeparam name="TTo">The implementation type.</typeparam>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegister<TFrom, TTo>(this IContainerRegistry containerRegistry)
+            where TTo : TFrom
+        {
+            return containerRegistry.TryRegister(typeof(TFrom), typeof(TTo));
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <typeparam name="T">The service type.</typeparam>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegister<T>(this IContainerRegistry containerRegistry)
+            where T : class
+        {
+            return containerRegistry.TryRegister(typeof(T), typeof(T));
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <param name="from">The service type.</param>
+        /// <param name="to">The implementation type.</param>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegisterScoped(this IContainerRegistry containerRegistry, Type from, Type to)
+        {
+            if (!containerRegistry.IsRegistered(from))
+                containerRegistry.RegisterScoped(from, to);
+
+            return containerRegistry;
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <typeparam name="T">The service type.</typeparam>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegisterScoped<T>(this IContainerRegistry containerRegistry)
+            where T : class
+        {
+            return containerRegistry.TryRegisterScoped(typeof(T), typeof(T));
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <typeparam name="TFrom">The service type.</typeparam>
+        /// <typeparam name="TTo">The implementation type.</typeparam>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegisterScoped<TFrom, TTo>(this IContainerRegistry containerRegistry)
+            where TTo : TFrom
+        {
+            return containerRegistry.TryRegisterScoped(typeof(TFrom), typeof(TTo));
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <param name="from">The service type.</param>
+        /// <param name="to">The implementation type.</param>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegisterSingleton(this IContainerRegistry containerRegistry, Type from, Type to)
+        {
+            if (!containerRegistry.IsRegistered(from))
+                containerRegistry.RegisterSingleton(from, to);
+
+            return containerRegistry;
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <typeparam name="TFrom">The service type.</typeparam>
+        /// <typeparam name="TTo">The implementation type.</typeparam>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegisterSingleton<TFrom, TTo>(this IContainerRegistry containerRegistry)
+            where TTo : TFrom
+        {
+            return containerRegistry.TryRegisterSingleton(typeof(TFrom), typeof(TTo));
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <typeparam name="T">The service type.</typeparam>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegisterSingleton<T>(this IContainerRegistry containerRegistry)
+            where T : class
+        {
+            return containerRegistry.TryRegisterSingleton(typeof(T), typeof(T));
+        }
+
+        /// <summary>
+        /// Will try to register the service if it has not already been registered
+        /// </summary>
+        /// <typeparam name="T">The service type.</typeparam>
+        /// <param name="containerRegistry">The <see cref="IContainerRegistry"/>.</param>
+        /// <param name="instance">An instance of the service.</param>
+        /// <returns>The <see cref="IContainerRegistry"/>.</returns>
+        public static IContainerRegistry TryRegisterInstance<T>(this IContainerRegistry containerRegistry, T instance)
+        {
+            if (!containerRegistry.IsRegistered<T>())
+                containerRegistry.RegisterInstance(instance);
+
+            return containerRegistry;
+        }
+
         /// <summary>
         /// Registers an instance of a given <see cref="Type"/>
         /// </summary>

src/Wpf/Prism.Wpf/PrismInitializationExtensions.cs

@@ -28,20 +28,20 @@ internal static void ConfigureViewModelLocator()
 
         internal static void RegisterRequiredTypes(this IContainerRegistry containerRegistry, IModuleCatalog moduleCatalog)
         {
-            containerRegistry.RegisterInstance(moduleCatalog);
-            containerRegistry.RegisterSingleton<IDialogService, DialogService>();
-            containerRegistry.RegisterSingleton<IModuleInitializer, ModuleInitializer>();
-            containerRegistry.RegisterSingleton<IModuleManager, ModuleManager>();
-            containerRegistry.RegisterSingleton<RegionAdapterMappings>();
-            containerRegistry.RegisterSingleton<IRegionManager, RegionManager>();
-            containerRegistry.RegisterSingleton<IRegionNavigationContentLoader, RegionNavigationContentLoader>();
-            containerRegistry.RegisterSingleton<IEventAggregator, EventAggregator>();
-            containerRegistry.RegisterSingleton<IRegionViewRegistry, RegionViewRegistry>();
-            containerRegistry.RegisterSingleton<IRegionBehaviorFactory, RegionBehaviorFactory>();
-            containerRegistry.Register<IRegionNavigationJournalEntry, RegionNavigationJournalEntry>();
-            containerRegistry.Register<IRegionNavigationJournal, RegionNavigationJournal>();
-            containerRegistry.Register<IRegionNavigationService, RegionNavigationService>();
-            containerRegistry.Register<IDialogWindow, DialogWindow>(); //default dialog host
+            containerRegistry.TryRegisterInstance(moduleCatalog);
+            containerRegistry.TryRegisterSingleton<IDialogService, DialogService>();
+            containerRegistry.TryRegisterSingleton<IModuleInitializer, ModuleInitializer>();
+            containerRegistry.TryRegisterSingleton<IModuleManager, ModuleManager>();
+            containerRegistry.TryRegisterSingleton<RegionAdapterMappings>();
+            containerRegistry.TryRegisterSingleton<IRegionManager, RegionManager>();
+            containerRegistry.TryRegisterSingleton<IRegionNavigationContentLoader, RegionNavigationContentLoader>();
+            containerRegistry.TryRegisterSingleton<IEventAggregator, EventAggregator>();
+            containerRegistry.TryRegisterSingleton<IRegionViewRegistry, RegionViewRegistry>();
+            containerRegistry.TryRegisterSingleton<IRegionBehaviorFactory, RegionBehaviorFactory>();
+            containerRegistry.TryRegister<IRegionNavigationJournalEntry, RegionNavigationJournalEntry>();
+            containerRegistry.TryRegister<IRegionNavigationJournal, RegionNavigationJournal>();
+            containerRegistry.TryRegister<IRegionNavigationService, RegionNavigationService>();
+            containerRegistry.TryRegister<IDialogWindow, DialogWindow>(); //default dialog host
         }
 
         internal static void RegisterDefaultRegionBehaviors(this IRegionBehaviorFactory regionBehaviors)

tests/Containers/Prism.Container.Shared/Tests/ContainerFixture.cs

@@ -741,5 +741,38 @@ public void RegisterInstance_RegistersIEnumerable()
         }
 
 #endif
+
+        [Fact]
+        public void TryRegisterTransientDoesNotReplaceOriginalRegistration()
+        {
+            Setup.CreateContainer();
+            Setup.Registry.TryRegister<IServiceA, ServiceA>();
+            Setup.Registry.TryRegister<IServiceA, CompositeService>();
+
+            var service = Setup.Container.Resolve<IServiceA>();
+            Assert.IsType<ServiceA>(service);
+        }
+
+        [Fact]
+        public void TryRegisterScopedDoesNotReplaceOriginalRegistration()
+        {
+            Setup.CreateContainer();
+            Setup.Registry.TryRegisterScoped<IServiceA, ServiceA>();
+            Setup.Registry.TryRegisterScoped<IServiceA, CompositeService>();
+
+            var service = Setup.Container.Resolve<IServiceA>();
+            Assert.IsType<ServiceA>(service);
+        }
+
+        [Fact]
+        public void TryRegisterSingletonDoesNotReplaceOriginalRegistration()
+        {
+            Setup.CreateContainer();
+            Setup.Registry.TryRegisterSingleton<IServiceA, ServiceA>();
+            Setup.Registry.TryRegisterSingleton<IServiceA, CompositeService>();
+
+            var service = Setup.Container.Resolve<IServiceA>();
+            Assert.IsType<ServiceA>(service);
+        }
     }
 }