Why Enumerable doesn't inherits from IEnumerable<T>
<p>I'm very confused about this issue and can't understand it.In the <code>Enumerable</code> Documentation, I read this:</p>

<blockquote>
  <p>that implement System.Collections.Generic.IEnumerable</p>
</blockquote>

<p>and some methods like <code>Select()</code> return <code>IEnumerable&lt;TSource&gt;</code> that we can use from other methods like <code>Where()</code> after using that.for example:</p>

<pre><code>names.Select(name =&gt; name).Where(name =&gt; name.Length &gt; 3 );
</code></pre>

<p>but <code>Enumerable</code> doesn't inherit from <code>IEnumerable&lt;T&gt;</code> and <code>IEnumerable&lt;T&gt;</code> doesn't contain <code>Select()</code>,<code>Where()</code> and etc too...</p>

<p>have i wrong ?<br />
or exists any reason for this?</p>
