// 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);
}