this parameter modifier in C#?
<p>I'm curious about this code snippet: </p>

<pre><code>public static class XNAExtensions
{
    /// &lt;summary&gt;
    /// Write a Point
    /// &lt;/summary&gt;
    public static void Write(this NetOutgoingMessage message, Point value)
    {
        message.Write(value.X);
        message.Write(value.Y);
    }
    // ...
};
</code></pre>

<p>What does the <code>this</code> keyword mean next to the parameter type? I can't seem to find any information about it anywhere, even in the C# specification.</p>
