Why middleware in ASP.NET Core requires specific semantics, but not an interface?
<p>As known, IApplicationBuilder of the method Configure (class Startup) in ASP.NET Core requires specific semantics (to have method 'Invoke' with input parameter of HttpContext type and Task as return value). But why it's not implemented as interface? I can write something like it:</p>

<pre><code>public class FakeMiddleware
{

}
</code></pre>

<p>and register it:</p>

<pre><code>    app.UseMiddleware&lt;FakeMiddleware&gt;();
</code></pre>

<p>and we'll get an runtime error. Of course, it's trivial thing and easy to be found and fix, but it's implemented so rough, without interface?</p>