#3: improve multiton usage:

- allow declaration of interfaces as scope, but still getting instance through implementation
- add new method `ClearMultitonInstances<T>()` that allows to clear the created multiton instances for a given type
- handle `ClearMultitonInstance<T>()` method in abstract factories and call the corresponding method in the IIocContainer
- update tests

LightweightIocContainer/Exceptions/IllegalAbstractMethodCreationException.cs

@@ -0,0 +1,26 @@
+// // Author: Gockner, Simon
+// // Created: 2019-06-28
+// // Copyright(c) 2019 SimonG. All Rights Reserved.
+
+using System;
+using System.Reflection;
+
+namespace LightweightIocContainer.Exceptions
+{
+    /// <summary>
+    /// The creation of the abstract method is illegal in its current state
+    /// </summary>
+    public class IllegalAbstractMethodCreationException : Exception
+    {
+        public IllegalAbstractMethodCreationException(string message, MethodInfo method)
+            : base(message)
+        {
+            Method = method;
+        }
+
+        /// <summary>
+        /// The Method whose creation is illegal
+        /// </summary>
+        public MethodInfo Method { get; }
+    }
+}

LightweightIocContainer/Interfaces/IIocContainer.cs

@@ -51,5 +51,11 @@ namespace LightweightIocContainer.Interfaces
         /// <returns>An instance of the given type</returns>
         /// <exception cref="InternalResolveException">Could not find function <see cref="IocContainer.ResolveInternal{T}"/></exception>
         object Resolve(Type type, object[] arguments);
+
+        /// <summary>
+        /// Clear the multiton instances of the given type from the registered multitons list
+        /// </summary>
+        /// <typeparam name="T">The Type to clear the multiton instances</typeparam>
+        void ClearMultitonInstances<T>();
     }
 }

LightweightIocContainer/IocContainer.cs

@@ -158,7 +158,7 @@ namespace LightweightIocContainer
                 throw new MultitonResolveException("Can not resolve multiton without arguments.", typeof(T));
 
             object scopeArgument = arguments[0];
-            if (scopeArgument.GetType() != registration.Scope)
+            if (scopeArgument.GetType() != registration.Scope && !registration.Scope.IsInstanceOfType(scopeArgument))
                 throw new MultitonResolveException($"Can not resolve multiton without the first argument being the scope (should be of type {registration.Scope}).", typeof(T));
 
             //if a multiton for the given scope exists return it
@@ -245,7 +245,22 @@ namespace LightweightIocContainer
             
             return null;
         }
-        
+
+        /// <summary>
+        /// Clear the multiton instances of the given type from the registered multitons list
+        /// </summary>
+        /// <typeparam name="T">The Type to clear the multiton instances</typeparam>
+        public void ClearMultitonInstances<T>()
+        {
+            var multitonInstance = _multitons.FirstOrDefault(m => m.type == typeof(T));
+
+            //it is allowed to clear a non existing multiton instance (don't throw an exception)
+            if (multitonInstance == default)
+                return;
+
+            _multitons.Remove(multitonInstance);
+        }
+
         public void Dispose()
         {
             _registrations.Clear();

LightweightIocContainer/LightweightIocContainer.xml

@@ -4,6 +4,16 @@
         <name>LightweightIocContainer</name>
     </assembly>
     <members>
+        <member name="T:LightweightIocContainer.Exceptions.IllegalAbstractMethodCreationException">
+            <summary>
+            The creation of the abstract method is illegal in its current state
+            </summary>
+        </member>
+        <member name="P:LightweightIocContainer.Exceptions.IllegalAbstractMethodCreationException.Method">
+            <summary>
+            The Method whose creation is illegal
+            </summary>
+        </member>
         <member name="T:LightweightIocContainer.Exceptions.InternalResolveException">
             <summary>
             An internal Error happened while the <see cref="T:LightweightIocContainer.Interfaces.IIocContainer"/> tried to resolve an instance
@@ -153,6 +163,12 @@
             <returns>An instance of the given type</returns>
             <exception cref="T:LightweightIocContainer.Exceptions.InternalResolveException">Could not find function <see cref="M:LightweightIocContainer.IocContainer.ResolveInternal``1(System.Object[])"/></exception>
         </member>
+        <member name="M:LightweightIocContainer.Interfaces.IIocContainer.ClearMultitonInstances``1">
+            <summary>
+            Clear the multiton instances of the given type from the registered multitons list
+            </summary>
+            <typeparam name="T">The Type to clear the multiton instances</typeparam>
+        </member>
         <member name="T:LightweightIocContainer.Interfaces.Installers.IAssemblyInstaller">
             <summary>
             An <see cref="T:LightweightIocContainer.Interfaces.Installers.IIocInstaller"/> that installs all <see cref="T:LightweightIocContainer.Interfaces.Installers.IIocInstaller"/>s for its given <see cref="T:System.Reflection.Assembly"/>
@@ -330,6 +346,12 @@
             <param name="arguments">The existing arguments</param>
             <returns>An array of all needed constructor arguments to create <param name="type"></param></returns>
         </member>
+        <member name="M:LightweightIocContainer.IocContainer.ClearMultitonInstances``1">
+            <summary>
+            Clear the multiton instances of the given type from the registered multitons list
+            </summary>
+            <typeparam name="T">The Type to clear the multiton instances</typeparam>
+        </member>
         <member name="T:LightweightIocContainer.Lifestyle">
             <summary>
             The Lifestyles that can be used for a <see cref="T:LightweightIocContainer.Interfaces.Registrations.IDefaultRegistration`1"/>
@@ -483,6 +505,7 @@
             Creates the factory from the given abstract factory type
             </summary>
             <exception cref="T:LightweightIocContainer.Exceptions.InvalidFactoryRegistrationException">Factory registration is invalid</exception>
+            <exception cref="T:LightweightIocContainer.Exceptions.IllegalAbstractMethodCreationException">Creation of abstract methods are illegal in their current state</exception>
         </member>
     </members>
 </doc>

LightweightIocContainer/Registrations/TypedFactoryRegistration.cs

@@ -21,6 +21,8 @@ namespace LightweightIocContainer.Registrations
     /// <typeparam name="TFactory">The type of the abstract typed factory</typeparam>
     public class TypedFactoryRegistration<TFactory> : ITypedFactoryRegistration<TFactory>
     {
+        private const string CLEAR_MULTITON_INSTANCE_METHOD_NAME = "ClearMultitonInstance";
+
         public TypedFactoryRegistration(Type factoryType, IIocContainer container)
         {
             InterfaceType = factoryType;
@@ -49,6 +51,7 @@ namespace LightweightIocContainer.Registrations
         /// Creates the factory from the given abstract factory type
         /// </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)
         {
             List<MethodInfo> createMethods = InterfaceType.GetMethods().Where(m => m.ReturnType != typeof(void)).ToList();
@@ -129,6 +132,41 @@ namespace LightweightIocContainer.Registrations
                 generator.Emit(OpCodes.Ret);
             }
 
+            //if factory contains a method to clear multiton instances
+            MethodInfo multitonClearMethod = InterfaceType.GetMethods().FirstOrDefault(m => m.Name.Equals(CLEAR_MULTITON_INSTANCE_METHOD_NAME));
+            if (multitonClearMethod != null)
+            {
+                //create a method that looks like this
+                //public void ClearMultitonInstance<typeToClear>()
+                //{
+                //    IIocContainer.ClearMultitonInstances<typeToClear>();
+                //}
+
+                if (multitonClearMethod.IsGenericMethod)
+                {
+                    Type typeToClear = multitonClearMethod.GetGenericArguments().FirstOrDefault();
+                    if (typeToClear == null)
+                        throw new IllegalAbstractMethodCreationException("No Type to clear specified.", multitonClearMethod);
+
+                    MethodBuilder multitonClearMethodBuilder = typeBuilder.DefineMethod(multitonClearMethod.Name, MethodAttributes.Public | MethodAttributes.Virtual,
+                        multitonClearMethod.ReturnType, null);
+                    multitonClearMethodBuilder.DefineGenericParameters(typeToClear.Name);
+
+                    typeBuilder.DefineMethodOverride(multitonClearMethodBuilder, multitonClearMethod);
+
+                    ILGenerator multitonClearGenerator = multitonClearMethodBuilder.GetILGenerator();
+                    multitonClearGenerator.Emit(OpCodes.Ldarg_0);
+                    multitonClearGenerator.Emit(OpCodes.Ldfld, containerFieldBuilder);
+
+                    multitonClearGenerator.EmitCall(OpCodes.Callvirt, typeof(IIocContainer).GetMethod(nameof(IIocContainer.ClearMultitonInstances))?.MakeGenericMethod(typeToClear), null);
+                    multitonClearGenerator.Emit(OpCodes.Ret);
+                }
+                else
+                {
+                    throw new IllegalAbstractMethodCreationException("No Type to clear specified.", multitonClearMethod);
+                }
+            }
+
             Factory.Factory = (TFactory) Activator.CreateInstance(typeBuilder.CreateTypeInfo().AsType(), container);
         }
     }

Test.LightweightIocContainer/IocContainerTest.cs

@@ -26,6 +26,8 @@ namespace Test.LightweightIocContainer
             ITest Create();
             ITest Create(string name);
             ITest Create(MultitonScope scope);
+
+            void ClearMultitonInstance<T>();
         }
 
         private interface ITestFactoryNoCreate
@@ -33,6 +35,13 @@ namespace Test.LightweightIocContainer
             
         }
 
+        private interface ITestFactoryNonGenericClear
+        {
+            ITest Create();
+
+            void ClearMultitonInstance();
+        }
+
         private class Test : ITest
         {
 
@@ -112,6 +121,14 @@ namespace Test.LightweightIocContainer
             Assert.Throws<InvalidFactoryRegistrationException>(() => iocContainer.Register(RegistrationFactory.RegisterFactory<ITestFactoryNoCreate>(iocContainer)));
         }
 
+        [Test]
+        public void TestRegisterFactoryClearMultitonsNonGeneric()
+        {
+            IIocContainer iocContainer = new IocContainer();
+
+            Assert.Throws<IllegalAbstractMethodCreationException>(() => iocContainer.Register(RegistrationFactory.RegisterFactory<ITestFactoryNonGenericClear>(iocContainer)));
+        }
+
         [Test]
         public void TestResolveNotRegistered()
         {
@@ -287,5 +304,35 @@ namespace Test.LightweightIocContainer
             Assert.AreNotSame(resolvedTest1, resolvedTest3);
             Assert.AreNotSame(resolvedTest2, resolvedTest3);
         }
+
+        [Test]
+        public void TestResolveMultitonFromFactoryClearInstances()
+        {
+            IIocContainer iocContainer = new IocContainer();
+            iocContainer.Register(RegistrationFactory.Register<ITest, Test, MultitonScope>());
+            iocContainer.Register(RegistrationFactory.RegisterFactory<ITestFactory>(iocContainer));
+
+            MultitonScope scope1 = new MultitonScope();
+            MultitonScope scope2 = new MultitonScope();
+
+            ITestFactory testFactory = iocContainer.Resolve<ITestFactory>();
+
+            ITest resolvedTest1 = testFactory.Create(scope1);
+            ITest resolvedTest2 = testFactory.Create(scope1);
+            ITest resolvedTest3 = testFactory.Create(scope2);
+
+            Assert.AreSame(resolvedTest1, resolvedTest2);
+            Assert.AreNotSame(resolvedTest1, resolvedTest3);
+            Assert.AreNotSame(resolvedTest2, resolvedTest3);
+
+            testFactory.ClearMultitonInstance<ITest>();
+
+            ITest resolvedTest4 = testFactory.Create(scope1);
+            ITest resolvedTest5 = testFactory.Create(scope2);
+
+            Assert.AreNotSame(resolvedTest1, resolvedTest4);
+            Assert.AreNotSame(resolvedTest2, resolvedTest4);
+            Assert.AreNotSame(resolvedTest3, resolvedTest5);
+        }
     }
 }