Relaying a request in asp.net (Forwarding a request)

I have an extension method on HttpResponseBase to copy an incoming request to an outgoing request.

Usage:

    var externalRequest = (HttpWebRequest)WebRequest.Create("http://stackoverflow.com");
    this.Request.CopyTo(externalRequest);
    var externalResponse = (HttpWebResponse)externalRequest.GetResponse();

Source:

/// <summary>
/// Copies all headers and content (except the URL) from an incoming to an outgoing
/// request.
/// </summary>
/// <param name="source">The request to copy from</param>
/// <param name="destination">The request to copy to</param>
public static void CopyTo(this HttpRequestBase source, HttpWebRequest destination)
{
    source.InputStream.Position = 0;
    destination.Method = source.HttpMethod;

    // Copy unrestricted headers (including cookies, if any)
    foreach (var headerKey in source.Headers.AllKeys)
    {
        switch (headerKey)
        {
            case "Connection":
            case "Content-Length":
            case "Date":
            case "Expect":
            case "Host":
            case "If-Modified-Since":
            case "Range":
            case "Transfer-Encoding":
            case "Proxy-Connection":
                // Let IIS handle these
                break;

            case "Accept":
            case "Content-Type":
            case "Referer":
            case "User-Agent":
                // Restricted - copied below
                break;

            default:
                destination.Headers[headerKey] = source.Headers[headerKey];
                break;
        }
    }

    // Copy restricted headers
    if (source.AcceptTypes.Any())
    {
        destination.Accept = string.Join(",", source.AcceptTypes);
    }
    destination.ContentType = source.ContentType;
    destination.Referer = source.UrlReferrer.AbsoluteUri;
    destination.UserAgent = source.UserAgent;

    // Copy content (if content body is allowed)
    if (source.HttpMethod != "GET"
        && source.HttpMethod != "HEAD"
        && source.ContentLength > 0)
    {
        var destinationStream = destination.GetRequestStream();
        source.InputStream.CopyTo(destinationStream);
        destinationStream.Close();
    }
}