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POCheck if a given event is subscribed, during runtime, using reflection
 

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    <p>Consider a class that has some events. This event list is going to grow. Some are optional. Others are required.</p> <p>To simplify some initial validation I have a custom attribute that marks an event as a required one. For example:</p> <pre><code> [RequiredEventSubscription("This event is required!")] public event EventHandler ServiceStarted; </code></pre> <p>So far so good. To validate all events, using reflection I iterate the event list and grab the custom attributes. But I need a way to determine if the event is subscribed or not.</p> <p>Without reflection the ServiceStarted.GetInvocationList does the job. But the event must come from this list: var eventList = this.GetType().GetEvents().ToList();</p> <p>Is there any way to check if a given event, from an event list, is subscribed using reflection?</p> <p>--[Update]-- Here's a possible solution based on Ami's answer:</p> <pre><code> private void CheckIfRequiredEventsAreSubscribed() { var eventList = GetType().GetEvents().ToList().Where(e =&gt; Attribute.IsDefined(e, typeof(RequiredEventSubscription))); StringBuilder exceptionMessage = new StringBuilder(); StringBuilder warnMessage = new StringBuilder(); foreach (var evt in eventList) { RequiredEventSubscription reqAttr = (RequiredEventSubscription) evt.GetCustomAttributes(typeof(RequiredEventSubscription), true).First(); var evtDelegate = this.GetType().GetField(evt.Name, BindingFlags.Instance | BindingFlags.NonPublic); if (evtDelegate.GetValue(this) == null) { warnMessage.AppendLine(reqAttr.warnMess); if (reqAttr.throwException) exceptionMessage.AppendLine(reqAttr.warnMess); } } if (warnMessage.Length &gt; 0) Console.WriteLine(warnMessage); if (exceptionMessage.Length &gt; 0) throw new RequiredEventSubscriptionException(exceptionMessage.ToString()); } </code></pre> <p>Many thanks!!</p>
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    1. COIMHO, if subscribing to an event is required, don't make it an event in the first place but a delegate parameter to the constructor of your class.
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      1. USDaniel Hilgarth
    2. COWhat is doing the validating, and what does "required" mean in this context? Required for whom/what?
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      1. USDavid Pope
    3. CO@Daniel, that was my first approach, but sending so many delegates throughout the code lead me to this experiment.
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