#54: enabled nullable

- fix nullable warnings

LightweightIocContainer/ActionExtension.cs

@@ -15,7 +15,7 @@ namespace LightweightIocContainer
         /// <typeparam name="T2">The <see cref="Type"/> of the given <see cref="Action{T2}"/>, has to implement <typeparamref name="T1"/></typeparam>
         /// <param name="action">The given <see cref="Action{T2}"/> to convert</param>
         /// <returns>An <see cref="Action{T1}"/> converted from the given <see cref="Action{T2}"/></returns>
-        public static Action<T1> Convert<T1, T2>(this Action<T2> action) where T1 : T2
+        public static Action<T1>? Convert<T1, T2>(this Action<T2>? action) where T1 : T2
         {
             if (action == null)
                 return null;

LightweightIocContainer/EnumerableExtension.cs

@@ -39,7 +39,7 @@ namespace LightweightIocContainer
         /// <param name="source">The given <see cref="IEnumerable{T}"/></param>
         /// <param name="predicate">A function to test each element for a condition</param>
         /// <returns>The first element of the <see cref="IEnumerable{T}"/> or a new instance of the given <see cref="Type"/> when no element is found</returns>
-        private static TSource TryGetFirst<TSource, TGiven>(this IEnumerable<TSource> source, Func<TSource, bool> predicate) where TGiven : TSource, new()
+        private static TSource TryGetFirst<TSource, TGiven>(this IEnumerable<TSource> source, Func<TSource, bool>? predicate) where TGiven : TSource, new()
         {
             try
             {

LightweightIocContainer/Exceptions/IocContainerException.cs

@@ -16,20 +16,15 @@ namespace LightweightIocContainer.Exceptions
         /// <summary>
         ///  A base <see cref="Exception"/> for the <see cref="LightweightIocContainer"/>
         /// </summary>
-        protected IocContainerException()
-        {
-
-        }
+        protected IocContainerException() => InnerExceptions = new List<Exception>();
 
         /// <summary>
         /// A base <see cref="Exception"/> for the <see cref="LightweightIocContainer"/>
         /// </summary>
         /// <param name="message">The message of the <see cref="Exception"/></param>
         protected IocContainerException(string message)
-            : base(message)
-        {
-
-        }
+            : base(message) =>
+            InnerExceptions = new List<Exception>();
 
         /// <summary>
         /// A base <see cref="Exception"/> for the <see cref="LightweightIocContainer"/>

LightweightIocContainer/Exceptions/NoMatchingConstructorFoundException.cs

@@ -4,7 +4,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 
 namespace LightweightIocContainer.Exceptions
 {
@@ -17,12 +16,11 @@ namespace LightweightIocContainer.Exceptions
         /// No matching constructor was found for the given or resolvable arguments
         /// </summary>
         /// <param name="type">The <see cref="Type"/> with no matching constructor</param>
-        /// <param name="exceptions">The inner exceptions of type <see cref="ConstructorNotMatchingException"/></param>
-        public NoMatchingConstructorFoundException(Type type, params ConstructorNotMatchingException[] exceptions)
+        public NoMatchingConstructorFoundException(Type type)
             : base($"No matching constructor for {type} found.")
         {
             Type = type;
-            InnerExceptions = exceptions == null ? new List<Exception>() : exceptions.OfType<Exception>().ToList();
+            InnerExceptions = new List<Exception>();
         }
 
 

LightweightIocContainer/Factories/TypedFactory.cs

@@ -24,7 +24,7 @@ namespace LightweightIocContainer.Factories
         /// The 
         /// </summary>
         /// <param name="container">The current instance of the <see cref="IIocContainer"/></param>
-        public TypedFactory(IIocContainer container) => CreateFactory(container);
+        public TypedFactory(IIocContainer container) => Factory = CreateFactory(container);
 
         /// <summary>
         /// The implemented abstract typed factory/>
@@ -36,7 +36,7 @@ namespace LightweightIocContainer.Factories
         /// </summary>
         /// <exception cref="InvalidFactoryRegistrationException">Factory registration is invalid</exception>
         /// <exception cref="IllegalAbstractMethodCreationException">Creation of abstract methods are illegal in their current state</exception>
-        private void CreateFactory(IIocContainer container)
+        private TFactory CreateFactory(IIocContainer container)
         {
             Type factoryType = typeof(TFactory);
             
@@ -92,7 +92,7 @@ namespace LightweightIocContainer.Factories
                 }
                 else
                 {
-                    MethodInfo emptyArray = typeof(Array).GetMethod(nameof(Array.Empty))?.MakeGenericMethod(typeof(object));
+                    MethodInfo? emptyArray = typeof(Array).GetMethod(nameof(Array.Empty))?.MakeGenericMethod(typeof(object));
                     generator.EmitCall(OpCodes.Call, emptyArray, null);
                 }
 
@@ -102,7 +102,7 @@ namespace LightweightIocContainer.Factories
             }
 
             //if factory contains a method to clear multiton instances
-            MethodInfo multitonClearMethod = factoryType.GetMethods().FirstOrDefault(m => m.Name.Equals(CLEAR_MULTITON_INSTANCE_METHOD_NAME));
+            MethodInfo? multitonClearMethod = factoryType.GetMethods().FirstOrDefault(m => m.Name.Equals(CLEAR_MULTITON_INSTANCE_METHOD_NAME));
             if (multitonClearMethod != null)
             {
                 //create a method that looks like this
@@ -113,7 +113,7 @@ namespace LightweightIocContainer.Factories
 
                 if (multitonClearMethod.IsGenericMethod)
                 {
-                    Type typeToClear = multitonClearMethod.GetGenericArguments().FirstOrDefault();
+                    Type? typeToClear = multitonClearMethod.GetGenericArguments().FirstOrDefault();
                     if (typeToClear == null)
                         throw new IllegalAbstractMethodCreationException("No Type to clear specified.", multitonClearMethod);
 
@@ -136,7 +136,7 @@ namespace LightweightIocContainer.Factories
                 }
             }
 
-            Factory = (TFactory) Activator.CreateInstance(typeBuilder.CreateTypeInfo().AsType(), container);
+            return (TFactory) Activator.CreateInstance(typeBuilder.CreateTypeInfo()?.AsType(), container);
         }
     }
 }

LightweightIocContainer/GenericMethodCaller.cs

@@ -24,10 +24,10 @@ namespace LightweightIocContainer
         /// <returns>The result of invoking the method</returns>
         /// <exception cref="GenericMethodNotFoundException">Could not find the generic method</exception>
         /// <exception cref="Exception">Any <see cref="Exception"/> thrown after invoking the generic method</exception>
-        public static object Call(object caller, string functionName, Type genericParameter, BindingFlags bindingFlags, params object[] parameters)
+        public static object Call(object caller, string functionName, Type genericParameter, BindingFlags bindingFlags, params object?[] parameters)
         {
-            MethodInfo method = caller.GetType().GetMethod(functionName, bindingFlags);
-            MethodInfo genericMethod = method?.MakeGenericMethod(genericParameter);
+            MethodInfo? method = caller.GetType().GetMethod(functionName, bindingFlags);
+            MethodInfo? genericMethod = method?.MakeGenericMethod(genericParameter);
 
             if (genericMethod == null)
                 throw new GenericMethodNotFoundException(functionName);
@@ -52,7 +52,7 @@ namespace LightweightIocContainer
         /// <returns>The result of invoking the method</returns>
         /// <exception cref="GenericMethodNotFoundException">Could not find the generic method</exception>
         /// <exception cref="Exception">Any <see cref="Exception"/> thrown after invoking the generic method</exception>
-        public static object CallPrivate(object caller, string functionName, Type genericParameter, params object[] parameters) =>
+        public static object CallPrivate(object caller, string functionName, Type genericParameter, params object?[] parameters) =>
             Call(caller, functionName, genericParameter, BindingFlags.NonPublic | BindingFlags.Instance, parameters);
     }
 }

LightweightIocContainer/Interfaces/Registrations/Fluent/IOnCreate.cs

@@ -16,7 +16,7 @@ namespace LightweightIocContainer.Interfaces.Registrations.Fluent
         /// This <see cref="Action"/> is invoked when an instance of this type is created.
         /// <para>Can be set in the <see cref="IIocInstaller"/> by calling <see cref="IOnCreate{TInterface, TImplementation}.OnCreate"/></para>
         /// </summary>
-        internal Action<object> OnCreateAction { get; }
+        internal Action<object?>? OnCreateAction { get; }
     }
 
     /// <summary>
@@ -31,6 +31,6 @@ namespace LightweightIocContainer.Interfaces.Registrations.Fluent
         /// </summary>
         /// <param name="action">The <see cref="Action{T}"/></param>
         /// <returns>The current instance of this <see cref="ITypedRegistration{TInterface,TImplementation}"/></returns>
-        ITypedRegistration<TInterface, TImplementation> OnCreate(Action<TImplementation> action);
+        ITypedRegistration<TInterface, TImplementation> OnCreate(Action<TImplementation?> action);
     }
 }

LightweightIocContainer/Interfaces/Registrations/Fluent/IWithFactory.cs

@@ -32,6 +32,6 @@ namespace LightweightIocContainer.Interfaces.Registrations.Fluent
         /// <summary>
         /// The Factory added with the <see cref="IWithFactory.WithFactory{TFactory}"/> method
         /// </summary>
-        ITypedFactory Factory { get; }
+        ITypedFactory? Factory { get; }
     }
 }

LightweightIocContainer/Interfaces/Registrations/Fluent/IWithParameters.cs

@@ -38,6 +38,6 @@ namespace LightweightIocContainer.Interfaces.Registrations.Fluent
         /// An <see cref="Array"/> of parameters that are used to <see cref="IocContainer.Resolve{T}()"/> an instance of this <see cref="IRegistration.InterfaceType"/>
         /// <para>Can be set in the <see cref="IIocInstaller"/> by calling <see cref="IWithParameters.WithParameters(object[])"/></para>
         /// </summary>
-        object[] Parameters { get; }
+        object[]? Parameters { get; }
     }
 }

LightweightIocContainer/Interfaces/Registrations/ISingleTypeRegistration.cs

@@ -15,7 +15,7 @@ namespace LightweightIocContainer.Interfaces.Registrations
         /// <summary>
         /// <see cref="Func{T,TResult}"/> that is invoked instead of creating an instance of this <see cref="Type"/> the default way
         /// </summary>
-        Func<IResolver, T> FactoryMethod { get; }
+        Func<IResolver, T>? FactoryMethod { get; }
 
         /// <summary>
         /// Pass a <see cref="Func{T,TResult}"/> that will be invoked instead of creating an instance of this <see cref="Type"/> the default way

LightweightIocContainer/IocContainer.cs

@@ -7,7 +7,6 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.CompilerServices;
-using JetBrains.Annotations;
 using LightweightIocContainer.Exceptions;
 using LightweightIocContainer.Interfaces;
 using LightweightIocContainer.Interfaces.Factories;
@@ -26,8 +25,8 @@ namespace LightweightIocContainer
     {
         private readonly RegistrationFactory _registrationFactory;
 
-        private readonly List<(Type type, object instance)> _singletons = new();
-        private readonly List<(Type type, Type scope, ConditionalWeakTable<object, object> instances)> _multitons = new();
+        private readonly List<(Type type, object? instance)> _singletons = new();
+        private readonly List<(Type type, Type scope, ConditionalWeakTable<object, object?> instances)> _multitons = new();
 
         /// <summary>
         /// The main container that carries all the <see cref="IRegistration"/>s and can resolve all the types you'll ever want
@@ -266,7 +265,7 @@ namespace LightweightIocContainer
         /// <param name="resolveStack">The current resolve stack</param>
         /// <returns>An instance of the given <see cref="Type"/></returns>
         /// <exception cref="InternalResolveException">Could not find function <see cref="ResolveInternal{T}"/></exception>
-        internal object Resolve(Type type, object[] arguments, List<Type> resolveStack) => 
+        internal object Resolve(Type type, object?[]? arguments, List<Type>? resolveStack) => 
             GenericMethodCaller.CallPrivate(this, nameof(ResolveInternal), type, arguments, resolveStack);
 
         /// <summary>
@@ -301,7 +300,7 @@ namespace LightweightIocContainer
         /// <returns>An instance of the given registered <see cref="Type"/></returns>
         /// <exception cref="TypeNotRegisteredException">The given <see cref="Type"/> is not registered in this <see cref="IocContainer"/></exception>
         /// <exception cref="UnknownRegistrationException">The registration for the given <see cref="Type"/> has an unknown <see cref="Type"/></exception>
-        private T ResolveInternal<T>(object[] arguments, List<Type> resolveStack = null)
+        private T ResolveInternal<T>(object[]? arguments, List<Type>? resolveStack = null)
         {
             IRegistration registration = FindRegistration<T>() ?? throw new TypeNotRegisteredException(typeof(T));
 
@@ -330,11 +329,11 @@ namespace LightweightIocContainer
         /// <param name="arguments">The arguments to resolve</param>
         /// <param name="resolveStack">The current resolve stack</param>
         /// <returns>An existing or newly created singleton instance of the given <see cref="Type"/></returns>
-        private T GetOrCreateSingletonInstance<T>(IRegistration registration, object[] arguments, List<Type> resolveStack)
+        private T GetOrCreateSingletonInstance<T>(IRegistration registration, object[]? arguments, List<Type> resolveStack)
         {
             Type type = GetType<T>(registration);
             
-            object instance = TryGetSingletonInstance(type);
+            object? instance = TryGetSingletonInstance(type);
             if (instance != null)
                 return (T) instance;
 
@@ -350,7 +349,7 @@ namespace LightweightIocContainer
         /// </summary>
         /// <param name="type">The given <see cref="Type"/></param>
         /// <returns>A singleton instance if existing for the given <see cref="Type"/>, null if not</returns>
-        private object TryGetSingletonInstance(Type type) => _singletons.FirstOrDefault(s => s.type == type).instance; //if a singleton instance exists return it
+        private object? TryGetSingletonInstance(Type type) => _singletons.FirstOrDefault(s => s.type == type).instance; //if a singleton instance exists return it
 
         /// <summary>
         /// Gets or creates a multiton instance of a given <see cref="Type"/>
@@ -362,7 +361,7 @@ namespace LightweightIocContainer
         /// <returns>An existing or newly created multiton instance of the given <see cref="Type"/></returns>
         /// <exception cref="MultitonResolveException">No arguments given</exception>
         /// <exception cref="MultitonResolveException">Scope argument not given</exception>
-        private T GetOrCreateMultitonInstance<T>(IMultitonRegistration registration, object[] arguments, List<Type> resolveStack)
+        private T GetOrCreateMultitonInstance<T>(IMultitonRegistration registration, object[]? arguments, List<Type> resolveStack)
         {
             if (arguments == null || !arguments.Any())
                 throw new MultitonResolveException("Can not resolve multiton without arguments.", typeof(T));
@@ -375,7 +374,7 @@ namespace LightweightIocContainer
             var instances = _multitons.FirstOrDefault(m => m.type == registration.ImplementationType && m.scope == registration.Scope).instances; //get instances for the given type and scope (use implementation type to resolve the correct instance for multiple multiton registrations as well)
             if (instances != null)
             {
-                if (instances.TryGetValue(scopeArgument, out object instance))
+                if (instances.TryGetValue(scopeArgument, out object? instance) && instance != null)
                     return (T) instance;
 
                 T createdInstance = CreateInstance<T>(registration, arguments, resolveStack);
@@ -386,7 +385,7 @@ namespace LightweightIocContainer
 
             T newInstance = CreateInstance<T>(registration, arguments, resolveStack);
 
-            ConditionalWeakTable<object, object> weakTable = new();
+            ConditionalWeakTable<object, object?> weakTable = new();
             weakTable.Add(scopeArgument, newInstance);
             
             _multitons.Add((registration.ImplementationType, registration.Scope, weakTable));
@@ -402,7 +401,7 @@ namespace LightweightIocContainer
         /// <param name="arguments">The constructor arguments</param>
         /// <param name="resolveStack">The current resolve stack</param>
         /// <returns>A newly created instance of the given <see cref="Type"/></returns>
-        private T CreateInstance<T>(IRegistration registration, object[] arguments, List<Type> resolveStack)
+        private T CreateInstance<T>(IRegistration registration, object[]? arguments, List<Type> resolveStack)
         {
             if (registration is IWithParametersInternal { Parameters: { } } registrationWithParameters)
                 arguments = UpdateArgumentsWithRegistrationParameters(registrationWithParameters, arguments);
@@ -450,8 +449,11 @@ namespace LightweightIocContainer
         /// <param name="registration">The <see cref="IRegistrationBase"/> of the given <see cref="Type"/></param>
         /// <param name="arguments">The constructor arguments</param>
         /// <returns>The argument list updated with the <see cref="IWithParametersInternal.Parameters"/></returns>
-        private object[] UpdateArgumentsWithRegistrationParameters(IWithParametersInternal registration, object[] arguments)
+        private object[]? UpdateArgumentsWithRegistrationParameters(IWithParametersInternal registration, object[]? arguments)
         {
+            if (registration.Parameters == null)
+                return arguments;
+            
             if (arguments != null && arguments.Any()) //if more arguments were passed to resolve
             {
                 int argumentsSize = registration.Parameters.Length + arguments.Length;
@@ -495,10 +497,9 @@ namespace LightweightIocContainer
         /// <param name="resolveStack">The current resolve stack</param>
         /// <returns>An array of all needed constructor arguments to create the <see cref="Type"/></returns>
         /// <exception cref="NoMatchingConstructorFoundException">No matching constructor was found for the given or resolvable arguments</exception>
-        [CanBeNull]
-        private object[] ResolveTypeCreationArguments(Type type, object[] arguments, List<Type> resolveStack)
+        private object[]? ResolveTypeCreationArguments(Type type, object[]? arguments, List<Type> resolveStack)
         {
-            (bool result, List<object> parameters, NoMatchingConstructorFoundException exception) = TryGetTypeResolveStack(type, arguments, resolveStack);
+            (bool result, List<object>? parameters, NoMatchingConstructorFoundException? exception) = TryGetTypeResolveStack(type, arguments, resolveStack);
             
             if (result)
             {
@@ -534,15 +535,15 @@ namespace LightweightIocContainer
         /// <para>parameters: The parameters needed to resolve the given <see cref="Type"/></para>
         /// <para>exception: A <see cref="NoMatchingConstructorFoundException"/> if no matching constructor was found</para>
         /// </returns>
-        private (bool result, List<object> parameters, NoMatchingConstructorFoundException exception) TryGetTypeResolveStack(Type type, object[] arguments, List<Type> resolveStack)
+        private (bool result, List<object>? parameters, NoMatchingConstructorFoundException? exception) TryGetTypeResolveStack(Type type, object[]? arguments, List<Type> resolveStack)
         {
-            NoMatchingConstructorFoundException noMatchingConstructorFoundException = null;
+            NoMatchingConstructorFoundException? noMatchingConstructorFoundException = null;
             
             //find best ctor
             List<ConstructorInfo> sortedConstructors = TryGetSortedConstructors(type);
             foreach (ConstructorInfo constructor in sortedConstructors)
             { 
-                (bool result, List<object> parameters, List<ConstructorNotMatchingException> exceptions) = TryGetConstructorResolveStack(constructor, arguments, resolveStack);
+                (bool result, List<object>? parameters, List<ConstructorNotMatchingException>? exceptions) = TryGetConstructorResolveStack(constructor, arguments, resolveStack);
 
                 if (result)
                     return (true, parameters, null);
@@ -566,7 +567,7 @@ namespace LightweightIocContainer
         /// <para>parameters: The parameters needed to resolve the given <see cref="Type"/></para>
         /// <para>exception: A List of <see cref="ConstructorNotMatchingException"/>s if the constructor is not matching</para>
         /// </returns>
-        private (bool result, List<object> parameters, List<ConstructorNotMatchingException> exceptions) TryGetConstructorResolveStack(ConstructorInfo constructor, object[] arguments, List<Type> resolveStack)
+        private (bool result, List<object>? parameters, List<ConstructorNotMatchingException>? exceptions) TryGetConstructorResolveStack(ConstructorInfo constructor, object[]? arguments, List<Type> resolveStack)
         {
             List<ParameterInfo> constructorParameters = constructor.GetParameters().ToList();
             if (!constructorParameters.Any())
@@ -575,7 +576,7 @@ namespace LightweightIocContainer
             List<ConstructorNotMatchingException> exceptions = new();
             List<object> parameters = new();
 
-            List<object> passedArguments = null;
+            List<object>? passedArguments = null;
             if (arguments != null)
                 passedArguments = new List<object>(arguments);
 
@@ -602,21 +603,21 @@ namespace LightweightIocContainer
 
                         Type registeredType = GetTypeNonGeneric(parameter.ParameterType, registration);
 
-                        object singletonInstance = TryGetSingletonInstance(registeredType);
+                        object? singletonInstance = TryGetSingletonInstance(registeredType);
                         if (singletonInstance != null)
                             fittingArgument = singletonInstance;
                         else
                         {
-                            object[] argumentsForRegistration = null;
+                            object[]? argumentsForRegistration = null;
                             if (registration is IWithParametersInternal { Parameters: { } } registrationWithParameters)
                                 argumentsForRegistration = UpdateArgumentsWithRegistrationParameters(registrationWithParameters, null);
 
-                            (bool result, List<object> parametersToResolve, NoMatchingConstructorFoundException exception) = 
+                            (bool result, List<object>? parametersToResolve, NoMatchingConstructorFoundException? exception) = 
                                 TryGetTypeResolveStack(registeredType, argumentsForRegistration, internalResolveStack);
 
                             if (result) 
                                 fittingArgument = new InternalToBeResolvedPlaceholder(registeredType, parametersToResolve);
-                            else
+                            else if (exception != null)
                                 exceptions.Add(new ConstructorNotMatchingException(constructor, exception));
                         }
                     }
@@ -648,18 +649,16 @@ namespace LightweightIocContainer
         /// </summary>
         /// <typeparam name="T">The given <see cref="Type"/></typeparam>
         /// <returns>The <see cref="IRegistration"/> for the given <see cref="Type"/></returns>
-        [CanBeNull]
-        private IRegistration FindRegistration<T>() => FindRegistration(typeof(T));
+        private IRegistration? FindRegistration<T>() => FindRegistration(typeof(T));
         
         /// <summary>
         /// Find the <see cref="IRegistration"/> for the given <see cref="Type"/>
         /// </summary>
         /// <param name="type">The given <see cref="Type"/></param>
         /// <returns>The <see cref="IRegistration"/> for the given <see cref="Type"/></returns>
-        [CanBeNull]
-        private IRegistration FindRegistration(Type type)
+        private IRegistration? FindRegistration(Type type)
         {
-            IRegistration registration = Registrations.FirstOrDefault(r => r.InterfaceType == type);
+            IRegistration? registration = Registrations.FirstOrDefault(r => r.InterfaceType == type);
             if (registration != null)
                 return registration;
 
@@ -721,7 +720,7 @@ namespace LightweightIocContainer
         /// <typeparam name="T">The given <see cref="Type"/></typeparam>
         /// <returns>The new resolve stack</returns>
         /// <exception cref="CircularDependencyException">A circular dependency was detected</exception>
-        private List<Type> CheckForCircularDependencies<T>(List<Type> resolveStack) => CheckForCircularDependencies(typeof(T), resolveStack);
+        private List<Type> CheckForCircularDependencies<T>(List<Type>? resolveStack) => CheckForCircularDependencies(typeof(T), resolveStack);
         
         /// <summary>
         /// Check the given resolve stack for circular dependencies
@@ -730,7 +729,7 @@ namespace LightweightIocContainer
         /// <param name="resolveStack">The given resolve stack</param>
         /// <returns>The new resolve stack</returns>
         /// <exception cref="CircularDependencyException">A circular dependency was detected</exception>
-        private List<Type> CheckForCircularDependencies(Type type, List<Type> resolveStack)
+        private List<Type> CheckForCircularDependencies(Type type, List<Type>? resolveStack)
         {
             if (resolveStack == null) //first resolve call
                 resolveStack = new List<Type> {type}; //create new stack and add the currently resolving type to the stack
@@ -748,7 +747,7 @@ namespace LightweightIocContainer
         /// <typeparam name="T">The <see cref="Type"/> to clear the multiton instances</typeparam>
         public void ClearMultitonInstances<T>()
         {
-            IRegistration registration = FindRegistration<T>();
+            IRegistration? registration = FindRegistration<T>();
             if (registration is not IMultitonRegistration multitonRegistration)
                 return;
             

LightweightIocContainer/LightweightIocContainer.csproj

@@ -14,6 +14,7 @@
     <FileVersion>3.0.0.0</FileVersion>
     <PackageLicenseFile>LICENSE.md</PackageLicenseFile>
     <PackageVersion>3.0.0-beta</PackageVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Debug|netstandard2.0|AnyCPU'">

LightweightIocContainer/LightweightIocContainer.xml

@@ -213,12 +213,11 @@
             No matching constructor was found for the given or resolvable arguments
             </summary>
         </member>
-        <member name="M:LightweightIocContainer.Exceptions.NoMatchingConstructorFoundException.#ctor(System.Type,LightweightIocContainer.Exceptions.ConstructorNotMatchingException[])">
+        <member name="M:LightweightIocContainer.Exceptions.NoMatchingConstructorFoundException.#ctor(System.Type)">
             <summary>
             No matching constructor was found for the given or resolvable arguments
             </summary>
             <param name="type">The <see cref="P:LightweightIocContainer.Exceptions.NoMatchingConstructorFoundException.Type"/> with no matching constructor</param>
-            <param name="exceptions">The inner exceptions of type <see cref="T:LightweightIocContainer.Exceptions.ConstructorNotMatchingException"/></param>
         </member>
         <member name="P:LightweightIocContainer.Exceptions.NoMatchingConstructorFoundException.Type">
             <summary>
@@ -946,6 +945,14 @@
             <returns>An instance of the given <see cref="T:System.Type"/></returns>
             <exception cref="T:LightweightIocContainer.Exceptions.InternalResolveException">Could not find function <see cref="M:LightweightIocContainer.IocContainer.ResolveInternal``1(System.Object[],System.Collections.Generic.List{System.Type})"/></exception>
         </member>
+        <member name="M:LightweightIocContainer.IocContainer.Resolve(LightweightIocContainer.ResolvePlaceholders.InternalToBeResolvedPlaceholder,System.Collections.Generic.List{System.Type})">
+            <summary>
+            Recursively resolve a <see cref="T:System.Type"/> with the given parameters for an <see cref="T:LightweightIocContainer.ResolvePlaceholders.InternalToBeResolvedPlaceholder"/>
+            </summary>
+            <param name="toBeResolvedPlaceholder">The <see cref="T:LightweightIocContainer.ResolvePlaceholders.InternalToBeResolvedPlaceholder"/> that includes the type and resolve stack</param>
+            <param name="resolveStack">The current resolve stack</param>
+            <returns>A recursively resolved instance of the given <see cref="T:System.Type"/></returns>
+        </member>
         <member name="M:LightweightIocContainer.IocContainer.ResolveInternal``1(System.Object[],System.Collections.Generic.List{System.Type})">
             <summary>
             Gets an instance of a given registered <see cref="T:System.Type"/>
@@ -967,6 +974,13 @@
             <param name="resolveStack">The current resolve stack</param>
             <returns>An existing or newly created singleton instance of the given <see cref="T:System.Type"/></returns>
         </member>
+        <member name="M:LightweightIocContainer.IocContainer.TryGetSingletonInstance(System.Type)">
+            <summary>
+            Try to get an existing singleton instance for a given <see cref="T:System.Type"/>
+            </summary>
+            <param name="type">The given <see cref="T:System.Type"/></param>
+            <returns>A singleton instance if existing for the given <see cref="T:System.Type"/>, null if not</returns>
+        </member>
         <member name="M:LightweightIocContainer.IocContainer.GetOrCreateMultitonInstance``1(LightweightIocContainer.Interfaces.Registrations.IMultitonRegistration,System.Object[],System.Collections.Generic.List{System.Type})">
             <summary>
             Gets or creates a multiton instance of a given <see cref="T:System.Type"/>
@@ -1007,6 +1021,90 @@
             <returns>An array of all needed constructor arguments to create the <see cref="T:System.Type"/></returns>
             <exception cref="T:LightweightIocContainer.Exceptions.NoMatchingConstructorFoundException">No matching constructor was found for the given or resolvable arguments</exception>
         </member>
+        <member name="M:LightweightIocContainer.IocContainer.TryGetTypeResolveStack(System.Type,System.Object[],System.Collections.Generic.List{System.Type})">
+            <summary>
+            Try to get the resolve stack for a given <see cref="T:System.Type"/>
+            </summary>
+            <param name="type">The given <see cref="T:System.Type"/></param>
+            <param name="arguments">The given arguments</param>
+            <param name="resolveStack">The current resolve stack</param>
+            <returns>
+            <para>result: True if successful, false if not</para>
+            <para>parameters: The parameters needed to resolve the given <see cref="T:System.Type"/></para>
+            <para>exception: A <see cref="T:LightweightIocContainer.Exceptions.NoMatchingConstructorFoundException"/> if no matching constructor was found</para>
+            </returns>
+        </member>
+        <member name="M:LightweightIocContainer.IocContainer.TryGetConstructorResolveStack(System.Reflection.ConstructorInfo,System.Object[],System.Collections.Generic.List{System.Type})">
+            <summary>
+            Try to get the resolve stack for a given constructor
+            </summary>
+            <param name="constructor">The <see cref="T:System.Reflection.ConstructorInfo"/> for the given constructor</param>
+            <param name="arguments">The given arguments</param>
+            <param name="resolveStack">The current resolve stack</param>
+            <returns>
+            <para>result: True if successful, false if not</para>
+            <para>parameters: The parameters needed to resolve the given <see cref="T:System.Type"/></para>
+            <para>exception: A List of <see cref="T:LightweightIocContainer.Exceptions.ConstructorNotMatchingException"/>s if the constructor is not matching</para>
+            </returns>
+        </member>
+        <member name="M:LightweightIocContainer.IocContainer.FindRegistration``1">
+            <summary>
+            Find the <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/> for the given <see cref="T:System.Type"/>
+            </summary>
+            <typeparam name="T">The given <see cref="T:System.Type"/></typeparam>
+            <returns>The <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/> for the given <see cref="T:System.Type"/></returns>
+        </member>
+        <member name="M:LightweightIocContainer.IocContainer.FindRegistration(System.Type)">
+            <summary>
+            Find the <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/> for the given <see cref="T:System.Type"/>
+            </summary>
+            <param name="type">The given <see cref="T:System.Type"/></param>
+            <returns>The <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/> for the given <see cref="T:System.Type"/></returns>
+        </member>
+        <member name="M:LightweightIocContainer.IocContainer.TryGetSortedConstructors(System.Type)">
+            <summary>
+            Try to get the sorted constructors for the given <see cref="T:System.Type"/>
+            </summary>
+            <param name="type">The given <see cref="T:System.Type"/></param>
+            <returns>A list of sorted <see cref="T:System.Reflection.ConstructorInfo"/> for the given <see cref="T:System.Type"/></returns>
+            <exception cref="T:LightweightIocContainer.Exceptions.NoPublicConstructorFoundException">No public constructor was found for the given <see cref="T:System.Type"/></exception>
+        </member>
+        <member name="M:LightweightIocContainer.IocContainer.GetType``1(LightweightIocContainer.Interfaces.Registrations.IRegistration)">
+            <summary>
+            Get the implementation type for the given <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/>
+            </summary>
+            <param name="registration">The given <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/></param>
+            <typeparam name="T">The given <see cref="T:System.Type"/> of the interface</typeparam>
+            <returns>The implementation <see cref="T:System.Type"/> for the given <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/></returns>
+            <exception cref="T:LightweightIocContainer.Exceptions.UnknownRegistrationException">Unknown <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/> passed</exception>
+        </member>
+        <member name="M:LightweightIocContainer.IocContainer.GetTypeNonGeneric(System.Type,LightweightIocContainer.Interfaces.Registrations.IRegistration)">
+            <summary>
+            Non generic method to get the implementation type for the given <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/>
+            </summary>
+            <param name="type">The given <see cref="T:System.Type"/> of the interface</param>
+            <param name="registration">The given <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/></param>
+            <returns>The implementation <see cref="T:System.Type"/> for the given <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/></returns>
+            <exception cref="T:LightweightIocContainer.Exceptions.UnknownRegistrationException">Unknown <see cref="T:LightweightIocContainer.Interfaces.Registrations.IRegistration"/> passed</exception>
+        </member>
+        <member name="M:LightweightIocContainer.IocContainer.CheckForCircularDependencies``1(System.Collections.Generic.List{System.Type})">
+            <summary>
+            Check the given resolve stack for circular dependencies
+            </summary>
+            <param name="resolveStack">The given resolve stack</param>
+            <typeparam name="T">The given <see cref="T:System.Type"/></typeparam>
+            <returns>The new resolve stack</returns>
+            <exception cref="T:LightweightIocContainer.Exceptions.CircularDependencyException">A circular dependency was detected</exception>
+        </member>
+        <member name="M:LightweightIocContainer.IocContainer.CheckForCircularDependencies(System.Type,System.Collections.Generic.List{System.Type})">
+            <summary>
+            Check the given resolve stack for circular dependencies
+            </summary>
+            <param name="type">The given <see cref="T:System.Type"/></param>
+            <param name="resolveStack">The given resolve stack</param>
+            <returns>The new resolve stack</returns>
+            <exception cref="T:LightweightIocContainer.Exceptions.CircularDependencyException">A circular dependency was detected</exception>
+        </member>
         <member name="M:LightweightIocContainer.IocContainer.ClearMultitonInstances``1">
             <summary>
             Clear the multiton instances of the given <see cref="T:System.Type"/> from the registered multitons list
@@ -1514,6 +1612,16 @@
             An internal placeholder that is used to hold types that need to be resolved during the resolving process
             </summary>
         </member>
+        <member name="P:LightweightIocContainer.ResolvePlaceholders.InternalToBeResolvedPlaceholder.ResolvedType">
+            <summary>
+            The <see cref="T:System.Type"/> to be resolved
+            </summary>
+        </member>
+        <member name="P:LightweightIocContainer.ResolvePlaceholders.InternalToBeResolvedPlaceholder.Parameters">
+            <summary>
+            The parameters needed to resolve the <see cref="P:LightweightIocContainer.ResolvePlaceholders.InternalToBeResolvedPlaceholder.ResolvedType"/>
+            </summary>
+        </member>
         <member name="M:LightweightIocContainer.TypeExtension.GetDefault(System.Type)">
             <summary>
             Returns the default value for a given <see cref="T:System.Type"/>

LightweightIocContainer/Registrations/MultipleMultitonRegistration.cs

@@ -45,7 +45,7 @@ namespace LightweightIocContainer.Registrations
         /// </summary>
         /// <param name="action">The <see cref="Action{T}"/></param>
         /// <returns>The current instance of this <see cref="ITypedRegistration{TInterface,TImplementation}"/></returns>
-        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation> action)
+        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation?> action)
         {
             foreach (IRegistration registration in Registrations)
             {

LightweightIocContainer/Registrations/MultipleRegistration.cs

@@ -24,10 +24,8 @@ namespace LightweightIocContainer.Registrations
         /// <param name="lifestyle">The <see cref="Lifestyle"/> of this <see cref="MultipleRegistration{TInterface1,TInterface2}"/></param>
         /// <param name="container">The current instance of the <see cref="IIocContainer"/></param>
         protected MultipleRegistration(Type interfaceType1, Type implementationType, Lifestyle lifestyle, IocContainer container)
-            : base(interfaceType1, implementationType, lifestyle, container)
-        {
-            
-        }
+            : base(interfaceType1, implementationType, lifestyle, container) =>
+            Registrations = new List<IRegistration>();
 
         /// <summary>
         /// A <see cref="List{T}"/> of <see cref="IRegistration"/>s that are registered within this <see cref="MultipleRegistration{TInterface1,TInterface2}"/>
@@ -66,7 +64,7 @@ namespace LightweightIocContainer.Registrations
         /// </summary>
         /// <param name="action">The <see cref="Action{T}"/></param>
         /// <returns>The current instance of this <see cref="ITypedRegistration{TInterface,TImplementation}"/></returns>
-        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation> action)
+        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation?> action)
         {
             foreach (IRegistration registration in Registrations)
             {
@@ -114,7 +112,7 @@ namespace LightweightIocContainer.Registrations
         /// </summary>
         /// <param name="action">The <see cref="Action{T}"/></param>
         /// <returns>The current instance of this <see cref="ITypedRegistration{TInterface,TImplementation}"/></returns>
-        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation> action)
+        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation?> action)
         {
             foreach (IRegistration registration in Registrations)
             {
@@ -167,7 +165,7 @@ namespace LightweightIocContainer.Registrations
         /// </summary>
         /// <param name="action">The <see cref="Action{T}"/></param>
         /// <returns>The current instance of this <see cref="ITypedRegistration{TInterface,TImplementation}"/></returns>
-        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation> action)
+        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation?> action)
         {
             foreach (IRegistration registration in Registrations)
             {
@@ -225,7 +223,7 @@ namespace LightweightIocContainer.Registrations
         /// </summary>
         /// <param name="action">The <see cref="Action{T}"/></param>
         /// <returns>The current instance of this <see cref="ITypedRegistration{TInterface,TImplementation}"/></returns>
-        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation> action)
+        public override ITypedRegistration<TInterface1, TImplementation> OnCreate(Action<TImplementation?> action)
         {
             foreach (IRegistration registration in Registrations)
             {

LightweightIocContainer/Registrations/RegistrationBase.cs

@@ -48,12 +48,12 @@ namespace LightweightIocContainer.Registrations
         /// An <see cref="Array"/> of parameters that are used to <see cref="IocContainer.Resolve{T}()"/> an instance of this <see cref="IRegistration.InterfaceType"/>
         /// <para>Can be set in the <see cref="IIocInstaller"/> by calling <see cref="WithParameters(object[])"/></para>
         /// </summary>
-        public object[] Parameters { get; private set; }
+        public object[]? Parameters { get; private set; }
         
         /// <summary>
         /// The Factory added with the <see cref="WithFactory{TFactory}"/> method
         /// </summary>
-        public ITypedFactory Factory { get; private set; }
+        public ITypedFactory? Factory { get; private set; }
 
         /// <summary>
         /// Pass parameters that will be used to <see cref="IocContainer.Resolve{T}()"/> an instance of this <see cref="IRegistration.InterfaceType"/>

LightweightIocContainer/Registrations/SingleTypeRegistration.cs

@@ -29,7 +29,7 @@ namespace LightweightIocContainer.Registrations
         /// <summary>
         /// <see cref="Func{T,TResult}"/> that is invoked instead of creating an instance of this <see cref="Type"/> the default way
         /// </summary>
-        public Func<IResolver, T> FactoryMethod { get; private set; }
+        public Func<IResolver, T>? FactoryMethod { get; private set; }
 
         /// <summary>
         /// Pass a <see cref="Func{T,TResult}"/> that will be invoked instead of creating an instance of this <see cref="Type"/> the default way

LightweightIocContainer/Registrations/TypedRegistration.cs

@@ -35,22 +35,22 @@ namespace LightweightIocContainer.Registrations
         /// This <see cref="Action"/> is invoked when an instance of this type is created.
         /// <para>Can be set in the <see cref="IIocInstaller"/> by calling <see cref="IOnCreate{TInterface,TImplementation}.OnCreate"/></para>
         /// </summary>
-        private Action<object> OnCreateAction { get; set; }
+        private Action<object?>? OnCreateAction { get; set; }
 
         /// <summary>
         /// This <see cref="Action"/> is invoked when an instance of this type is created.
         /// <para>Can be set in the <see cref="IIocInstaller"/> by calling <see cref="IOnCreate{TInterface,TImplementation}.OnCreate"/></para>
         /// </summary>
-        Action<object> IOnCreate.OnCreateAction => OnCreateAction;
+        Action<object?>? IOnCreate.OnCreateAction => OnCreateAction;
 
         /// <summary>
         /// Pass an <see cref="Action{T}"/> that will be invoked when an instance of this type is created
         /// </summary>
         /// <param name="action">The <see cref="Action{T}"/></param>
         /// <returns>The current instance of this <see cref="ITypedRegistration{TInterface,TImplementation}"/></returns>
-        public virtual ITypedRegistration<TInterface, TImplementation> OnCreate(Action<TImplementation> action)
+        public virtual ITypedRegistration<TInterface, TImplementation> OnCreate(Action<TImplementation?> action)
         {
-            OnCreateAction = a => action((TImplementation) a);
+            OnCreateAction = a => action((TImplementation?) a);
             return this;
         }
     }

LightweightIocContainer/ResolvePlaceholders/InternalToBeResolvedPlaceholder.cs

@@ -12,7 +12,7 @@ namespace LightweightIocContainer.ResolvePlaceholders
     /// </summary>
     internal class InternalToBeResolvedPlaceholder
     {
-        public InternalToBeResolvedPlaceholder(Type resolvedType, List<object> parameters)
+        public InternalToBeResolvedPlaceholder(Type resolvedType, List<object>? parameters)
         {
             ResolvedType = resolvedType;
             Parameters = parameters;
@@ -26,6 +26,6 @@ namespace LightweightIocContainer.ResolvePlaceholders
         /// <summary>
         /// The parameters needed to resolve the <see cref="ResolvedType"/>
         /// </summary>
-        public List<object> Parameters { get; }
+        public List<object>? Parameters { get; }
     }
 }

LightweightIocContainer/TypeExtension.cs

@@ -13,6 +13,6 @@ namespace LightweightIocContainer
         /// </summary>
         /// <param name="type">The given <see cref="Type"/></param>
         /// <returns>The default value for the given <see cref="Type"/></returns>
-        public static object GetDefault(this Type type) => type.IsValueType ? Activator.CreateInstance(type) : null;
+        public static object? GetDefault(this Type type) => type.IsValueType ? Activator.CreateInstance(type) : null;
     }
 }

LightweightIocContainer/Validation/IocValidator.cs

@@ -16,7 +16,7 @@ namespace LightweightIocContainer.Validation
     public class IocValidator
     {
         private readonly IocContainer _iocContainer;
-        private readonly List<(Type type, object parameter)> _parameters;
+        private readonly List<(Type type, object? parameter)> _parameters;
 
         /// <summary>
         /// Validator for your <see cref="IocContainer"/> to check if everything can be resolved with your current setup
@@ -25,7 +25,7 @@ namespace LightweightIocContainer.Validation
         public IocValidator(IocContainer iocContainer)
         {
             _iocContainer = iocContainer;
-            _parameters = new List<(Type, object)>();
+            _parameters = new List<(Type, object?)>();
         }
 
         /// <summary>
@@ -67,7 +67,7 @@ namespace LightweightIocContainer.Validation
                 throw new AggregateException("Validation failed.", validationExceptions);
         }
 
-        private void TryResolve(Type type, object[] arguments, List<Exception> validationExceptions)
+        private void TryResolve(Type type, object?[]? arguments, List<Exception> validationExceptions)
         {
             try
             {