带 ref / out 参数的动态事件订阅

Question

I have been using an expression tree to create a delegate and subscribe to any event with an Action<Object[]> , where all the event parameters are converted to an array of objects. This has been working fine until now, that I need to subscribe to an event with an out/ref parameter and I need to set the value of this parameter.

Is there a way to use something similar to the expression tree and subscribe to any event, but still be able to set/return values to the object that raised the event?

Expression tree to create a delegate:

public static Delegate CreateProxyWithDynamicParameters(this EventInfo EventInfo, Action<object[]> Action)
{
        var EventHandlerType = EventInfo.EventHandlerType;
        var InvokeMethodInfo = EventHandlerType.GetMethod("Invoke");

        var Parameters = InvokeMethodInfo.GetParameters().Select(Parameter => Expression.Parameter(Parameter.ParameterType, Parameter.Name)).ToArray();

        var ConvertedParameters = Parameters.Select(Parameter => Expression.Convert(Parameter, typeof(object))).Cast<Expression>().ToArray();

        var NewArrayInit = Expression.NewArrayInit(typeof(object), ConvertedParameters);

        var Body = Expression.Call(Expression.Constant(Action), "Invoke", null, NewArrayInit);
        var lambdaExpression = Expression.Lambda(Body, Parameters);

        return Delegate.CreateDelegate(EventInfo.EventHandlerType, lambdaExpression.Compile(), InvokeMethodInfo.Name, ignoreCase: false);
}

Subscription with the delegate:

protected static void AddEvent<TMessage>(EventInfo eventInfo) where TMessage : EventArgs
{
        void EventAction(object[] e)
        {
            // Run some event code.
        }

        var @delegate = eventInfo.CreateProxyWithDynamicParameters(EventAction);
        DelegateDictionary[typeof(TMessage)] = @delegate;

        eventInfo.AddEventHandler(x.Target, @delegate);
}

Edit:

Here is a vanilla simple. Where I need to set the HandlingCode parameter.

InventorApplication.ApplicationEvents.OnSaveDocument += ApplicationEvents_OnSaveDocument;

private void ApplicationEvents_OnSaveDocument(_Document DocumentObject, EventTimingEnum BeforeOrAfter, NameValueMap Context, out HandlingCodeEnum HandlingCode)
{
    HandlingCode = HandlingCodeEnum.kEventHandled;
}

Answer 1

You are going to struggle to do this with Expression , because Expression likes to be able to run things via reflection for fallback, and it can't handle refs via reflection. You might be able to do it via raw IL, but... that's getting messier and messier.

Frankly, this event API is making life hard for you. If you control that API, I strongly suggest using the more idiomatic (object sender, SomeEventArgs args) where SomeEventArgs: EventArgs . Your SomeEventArgs would then have properties for all the things you're trying to pass as parameters, and the interested code can just do:

args.HandlingCode = ...

to assign a value.