EmptyInterface.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>
<overview>
<p>Empty interfaces are often used as a way of marking particular classes.</p>

</overview>
<recommendation>
<p>In some languages, using a marker interface is a useful design pattern, but in C# it is better to 
use custom attributes. Marker interfaces are always inherited and so they cannot be 
applied to a single class without applying it to all subclasses. Custom attributes do 
not have this limitation.</p>

</recommendation>
<example>
<p>In this example, the <code>IsPrintable</code> interface has no defined methods and is simply 
being used as a marker.</p>
<sample src="EmptyInterfaceBad.cs" />

<p>The following example is better because it uses attributes instead.</p>
<sample src="EmptyInterfaceGood.cs" />

</example>
<references>

  <li>Wikipedia: <a href="http://en.wikipedia.org/wiki/Marker_interface_pattern">Marker interface pattern</a></li>
  <li>Microsoft: <a href="https://docs.microsoft.com/en-us/dotnet/csharp/tutorials/attributes">Using Attributes in C#</a></li>


</references>
</qhelp>