// Addes a new method to the class that can unsubscribe a weak event handler from the event delegate // E.g. #pragma warning disable S125 // Sections of code should not be "commented out" // [CompilerGenerated] // private void <event name>_Weak_Unsubscribe(EventHandler< eventargsType > weh) // { // this.EventDelegate = (<event type>) Delegate.Remove(this.EventDelegate, (<event type>)weh); // } #pragma warning restore S125 // Sections of code should not be "commented out" // This is used as a call back by the weak event handler to clean up when the target is garbage collected. public MethodDefinition AddUnsubscribeMethod() { // private void <event name>_Weak_Unsubscribe(EventHandler< eventargsType > weh) string unsubscribeMethodName = string.Format(CultureInfo.InvariantCulture, "<{0}>_Weak_Unsubscribe", _eventDelegate.Name); MethodDefinition unsubscribe = new MethodDefinition(unsubscribeMethodName, GetUnsubscribeMethodAttributes(), _eventDelegate.Module.TypeSystem.Void); unsubscribe.Parameters.Add(new ParameterDefinition(_closedGenericEventHandler)); // [CompilerGenerated] unsubscribe.CustomAttributes.Add(_moduleimporter.CompilerGeneratedAttribute); _eventDelegate.DeclaringType.Methods.Add(unsubscribe); var rootEmitter = new EmptyEmitter(unsubscribe, _moduleimporter); var weakHandler = rootEmitter.LoadMethodFirstArg(); if (!_isGenericHandler) { weakHandler = rootEmitter.DelegateConvert(weakHandler, _eventDelegate.FieldType); } var removeFromFieldDelegate = rootEmitter.CallDelegateRemove(rootEmitter.LoadField(_eventDelegate), weakHandler); var compatibleHandler = removeFromFieldDelegate; if (!_isGenericHandler) { compatibleHandler = rootEmitter.DelegateConvert(removeFromFieldDelegate, _eventDelegate.FieldType); } var instructions = rootEmitter.StoreField(compatibleHandler, _eventDelegate).Return(); unsubscribe.InsertInstructions(instructions, 0); return unsubscribe; }
#pragma warning disable S125 // Sections of code should not be "commented out" // <event type> b = (<event type>)FindWeak(<source delegate>, (EventHandler< eventargsType >)value); #pragma warning restore S125 // Sections of code should not be "commented out" public ILEmitter GenerateFindWeakIl(MethodDefinition method, VariableDefinition weakEventHandler) { var rootEmitter = new EmptyEmitter(method, _moduleimporter); var handler = rootEmitter.LoadMethodFirstArg(); if (!_isGenericHandler) { handler = rootEmitter.DelegateConvert(handler, _closedGenericEventHandler); } var callFindWeak = rootEmitter.FindWeak(_closedGenericEventHandler, rootEmitter.LoadField(_eventDelegate), handler); if (!_isGenericHandler) { return rootEmitter.Store(weakEventHandler, rootEmitter.DelegateConvert(callFindWeak, _eventDelegate.FieldType)); } return rootEmitter.Store(weakEventHandler, callFindWeak); }
// Wrap the method parameter in a weak event handler and store in a variable. #pragma warning disable S125 // Sections of code should not be "commented out" // i.e. <event type> b = (EventHandler)MakeWeak((EventHandler< eventargsType >)value, new Action<(EventHandler< eventargsType >)>(this.<woven unsubscribe action>)); #pragma warning restore S125 // Sections of code should not be "commented out" public ILEmitter GenerateMakeWeakIl(MethodDefinition method, MethodDefinition unsubscribe, VariableDefinition weakEventHandler) { var rootEmitter = new EmptyEmitter(method, _moduleimporter); var unsubscribeAction = rootEmitter.NewObject(_moduleimporter.ActionOpenCtor.MakeDeclaringTypeClosedGeneric(_closedGenericEventHandler), rootEmitter.LoadMethod(unsubscribe)); ILEmitter genericHandler = rootEmitter.LoadMethodFirstArg(); if (!_isGenericHandler) { genericHandler = rootEmitter.DelegateConvert(genericHandler, _closedGenericEventHandler); } var genericWeakHandler = rootEmitter.MakeWeak(_closedGenericEventHandler, genericHandler, unsubscribeAction); if (!_isGenericHandler) { return rootEmitter.Store(weakEventHandler, rootEmitter.DelegateConvert(genericWeakHandler, _eventDelegate.FieldType)); } return rootEmitter.Store(weakEventHandler, genericWeakHandler); }