Use of the using keyword in C#
<p>In my background in C++ I was a supporter of using the scope resolution operator, for example</p>

<pre><code>class Foo
{
    std::list&lt;int&gt;  m_list;
    ...
}
</code></pre>

<p>for external libraries, to keep clear which library you were using.</p>

<p>Now in C# I don't know if there's a rule of thumb or a best practice to know which packages should be included via the using keyword and which classes should be fully qualified. I suppose that this can be a subjetive issue, but would like to know the most extended practices.</p>
