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copied!<p>Because when you define an <a href="http://msdn.microsoft.com/en-us/library/8627sbea%28v=vs.110%29.aspx" rel="nofollow"><code>event</code></a>, with the <code>event SomeHandler SomeEvent</code> syntax, it default-defines <a href="http://msdn.microsoft.com/en-us/library/cc713648.aspx" rel="nofollow"><code>add</code> and <code>remove</code></a> for you. The point here is that the <em>only</em> way you publicly interact with an <code>event</code> is through <code>add</code> and <code>remove</code> (accessed by <code>+=</code> and <code>-=</code>, respectively). The language does not allow a "reset all" action, which is why <code>=</code> is not allowed.</p> <p>To address the more underlying question of a "design choice" for this...I suppose the driving force is that the <em>contract</em> of an <code>event</code> -- a multicast model where subscribers are free to add and remove their subscriptions. Allowing anyone to unsubscribe all subscribers would go against that contract and allowing only one subscriber <em>isn't</em> the contract.</p> <p><strong>Addendum:</strong> It looks like what you're looking for is the ability to expose the delegate directly, which can be done if you just rely on .NET's multicast delegate syntax. It looks a lot like the <code>event</code> syntax, but allows for clearing with <code>=</code> and is even smart enough to understand <code>+=</code> on a <code>null</code> <code>delegate</code> (see <a href="http://ideone.com/xdBG6" rel="nofollow">output</a>):</p> <pre><code>public delegate void F(int x); public static void Main() { F f = null; f += x => System.Console.WriteLine("First: {0}", x); f += x => System.Console.WriteLine("Second: {0}", x); f(5); } </code></pre> <p>Alternatively, you could use the long form of <code>event</code> with your <code>add</code>/<code>remove</code> hitting an internal list and provide a method that allows for clearing that list. </p>

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