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copied!<p>The question what the handler "returns" (better phrased: what content the handler writes) has nothing to do with the <code>IsReusable</code> property. This property makes a statement about the thread-safety of your code, not about whether the content can change. For example, a handler that writes <code>DateTime.Now</code> would be reusable. A handler that has an <code>SqlConnection</code> field and reads unchanging data would not be reusable because the connection is not thread-safe even if the data read is always the same.</p> <p>Context switching also has nothing to do with this because on a multi-core box no context switch is necessary to cause concurrency. What you mean is "thread-safety" with respect to concurrent invocations of <code>ProcessRequest</code> on the same instance of your <code>IHttpHandler</code> derived class.</p> <p>Now some practical advice: always have <code>IsReusable</code> return false and ensure that your handler class is cheap to allocate and does not bring tons of garbage with it. GC'ing a <em>single object</em> is <em>nothing</em>! My guess is the <code>IsReusable</code> property was created to give ASP.NET an artificial advantage in toy benchmarks, or to support poorly architected handlers that are expensive to create.</p> <p>If you have expensive resources (like caches) store them elsewhere (in a static field maybe).</p> <p>An easy way to obtain thread-safety is to not share anything. In that sense, don't share the handler.</p> <p><strong>TL;DR:</strong> Set <code>IsReusable</code> to false and move on. Nothing to see here. This is just a confusing design flaw in ASP.NET.</p>

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