var pageHandler = this.ViewContext.HttpContext.Handler.GetPageHandler();
    foreach (var c in pageHandler.Header.Controls)
    {
        if (c != null && c is System.Web.UI.HtmlControls.HtmlLink)
        {
            System.Web.UI.HtmlControls.HtmlLink mylink = (System.Web.UI.HtmlControls.HtmlLink)c;
            if (mylink.Attributes["rel"] == "canonical")
            {
                pageHandler.Header.Controls.Remove(mylink);
            }
        }
    }