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copied!<p>Your code has a few problems (some you and others have identified):</p> <ul> <li>The anonymous delegate cannot be removed from the event as coded.</li> <li>The anonymous delegate will live longer than the life of the method calling it because you've added it to <strong>FoundStep</strong> which is a member of <strong>this</strong>.</li> <li>Every entry into <strong>FindStepsByType</strong> adds another anonymous delegate to <strong>FoundStep</strong>.</li> <li>The anonymous delegate is a closure and effectively extends the lifetime of <strong>retval</strong>, so even if you stop referencing <strong>retval</strong> elsewhere in your code, it's still held by the anonymous delegate.</li> </ul> <p>To fix this, and still use an anonymous delegate, assign it to a local variable, and then remove the handler inside a <strong>finally</strong> block (necessary in case the handler throws an exception):</p> <pre><code> public List<IWFResourceInstance> FindStepsByType(IWFResource res) { List<IWFResourceInstance> retval = new List<IWFResourceInstance>(); EventHandler<WalkerStepEventArgs> handler = (sender, e) => { if (e.Step.ResourceType == res) retval.Add(e.Step); }; this.FoundStep += handler; try { this.Start(); } finally { this.FoundStep -= handler; } return retval; } </code></pre> <p>With C# 7.0+ you can replace the anonymous delegate with a local function, achieving the same effect:</p> <pre><code> public List<IWFResourceInstance> FindStepsByType(IWFResource res) { var retval = new List<IWFResourceInstance>(); void Handler(object sender, WalkerStepEventArgs e) { if (e.Step.ResourceType == res) retval.Add(e.Step); } FoundStep += Handler; try { this.Start(); } finally { FoundStep -= Handler; } return retval; } </code></pre>

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