Extension for a string returns unexpected value for that string in C#
<p>Maybe the question sound not good or too simple. But not for me in this case.</p>

<p>My problem is:
I created an extension for string, like</p>

<pre><code>public static void SetString( this string aString, string anotherString ) {

         aString = anotherString ;

         // process info for that string ... (database, files, etc)
      }
</code></pre>

<p>If I call that extension like:</p>

<pre><code>string anExistingString = "123";
anExistingString.SetString("Other value");

Console.Write(anExistingString);
</code></pre>

<p>but returns <code>123</code> instead of <code>Other value</code>...</p>

<p>Where is my mistake ?</p>
