Give "this" as default value of class method
<p>I want to use <code>this</code> as default value of class method as this code:</p>

<pre><code>public class Article
 {
    public int Id;//PK
    public String Author;//can be empty=anonymous
    public int? ToPublishDate;
    public String Summery;
    public String Content;
    public int RegDate;
    public Boolean Publish;

    private Boolean write(Article article=this,long position)
    {
        return true;
    }
 }
</code></pre>

<p>but on <code>this</code> give me this error:</p>

<blockquote>
  <p>Default parameter value for 'article' must be compile-time constant.</p>
</blockquote>

<p>Why this error occurs and how can I fix it?       </p>
