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POIs there a way to simplify this reflective delegate code in C#?
 

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  1. POIs there a way to simplify this reflective delegate code in C#?
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    <p>In <a href="https://stackoverflow.com/a/12867132/171121">this</a> response, I came up with the following helper method that could be reused by different <code>Task</code> creators to convert events into task completion sources.</p> <pre><code>// Helper method static Task&lt;T&gt; TaskFromEventHelper&lt;T&gt;(object target, string eventName, Func&lt;TaskCompletionSource&lt;T&gt;, object&gt; resultSetterFactory) { var tcs = new TaskCompletionSource&lt;T&gt;(); var addMethod = target.GetType().GetEvent(eventName).GetAddMethod(); var delegateType = addMethod.GetParameters()[0].ParameterType; var d = Delegate.CreateDelegate(delegateType, resultSetterFactory(tcs), "Invoke"); addMethod.Invoke(target, new object[] {d}); return tcs.Task; } // Empty events (Action style) static Task TaskFromEvent(object target, string eventName) { return TaskFromEventHelper(target, eventName, (Func&lt;TaskCompletionSource&lt;object&gt;, object&gt;)(tcs =&gt; (Action)(() =&gt; tcs.SetResult(null)))); } // One-value events (Action&lt;T&gt; style) static Task&lt;T&gt; TaskFromEvent&lt;T&gt;(object target, string eventName) { return TaskFromEventHelper(target, eventName, (Func&lt;TaskCompletionSource&lt;T&gt;, object&gt;)(tcs =&gt; (Action&lt;T&gt;)(tcs.SetResult))); } // Two-value events (Action&lt;T1, T2&gt; or EventHandler style) static Task&lt;Tuple&lt;T1, T2&gt;&gt; TaskFromEvent&lt;T1, T2&gt;(object target, string eventName) { return TaskFromEventHelper(target, eventName, (Func&lt;TaskCompletionSource&lt;Tuple&lt;T1, T2&gt;&gt;, object&gt;)(tcs =&gt; (Action&lt;T1, T2&gt;)((t1, t2) =&gt; tcs.SetResult(Tuple.Create(t1, t2))))); } </code></pre> <p>In each of the three examples I gave that use the helper method, there's a <code>tcs.SetResult</code> component, which makes me think there's a way to move that to the helper method too, which might perhaps simplify the signatures, so that perhaps the helper method would just have to accept a <code>Func&lt;?, T&gt;</code>, where that <code>Func</code> would take the output of the <code>event</code> and convert it to whatever <code>tcs.SetResult</code> takes. </p> <p>i.e., I'm thinking there must be a way to create a helper so I can write it as</p> <pre><code>// Empty events (Action style) static Task TaskFromEvent(object target, string eventName) { return TaskFromEventHelper&lt;object&gt;(target, eventName, new Func&lt;object&gt;(() =&gt; null)); } // One-value events (Action&lt;T&gt; style) static Task&lt;T&gt; TaskFromEvent&lt;T&gt;(object target, string eventName) { return TaskFromEventHelper&lt;T&gt;(target, eventName, new Func&lt;T, T&gt;(t =&gt; t)); } // Two-value events (Action&lt;T1, T2&gt; or EventHandler style) static Task&lt;Tuple&lt;T1, T2&gt;&gt; TaskFromEvent&lt;T1, T2&gt;(object target, string eventName) { return TaskFromEventHelper&lt;Tuple&lt;T1, T2&gt;&gt;(target, eventName, new Func&lt;T1, T2, Tuple&lt;T1, T2&gt;&gt;(Tuple.Create)); } </code></pre> <p>, but that's why I don't know the <code>?</code> in <code>Func&lt;?, T&gt;</code> above. This one for example needs <code>?</code> to be <em>two</em> parameters. Could it be passed in as <code>object</code> somehow? I have a feeling it could be possible, but if so it needs some real reflection magic.</p>
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