Как неявно преобразовать тип System.Delegate в WebPageManager

У меня ошибка в этом коде. Я не могу неявно преобразовать тип System.Delegate в WebPageManager в последней строке. Как я могу это сделать?

public WebCrawler(string startUri, string baseUri, int maximumUrlAllowed, bool keepWebContent, WebPageManager webPageManager)
{
    this.StartUri = new Uri(startUri);

    // In future this could be null and will process cross-site, but for now must exist
    if ((baseUri == null || baseUri.Trim().Length == 0))
    {
        this.BaseUri = new Uri(this.StartUri.GetLeftPart(UriPartial.Authority));
    }
    else
    {
        this.BaseUri = new Uri(baseUri);
    }

    this.MaximumUrlAllowed = maximumUrlAllowed;
    this.KeepWebContent = keepWebContent;

    m_webPagesPending = new Queue();
    mWebPages = new Hashtable();

    mWebPageManager = webPageManager;

    webPageManager.WebPageContentHandler = Delegate.Combine(webPageManager.WebPageContentHandler, new WebPageContentDelegate(this.HandleLinks));
}