Add CSS and JS references in Sandbox

These helper methods use javascript to dynamically load js and css resources and work within Sandbox Web Parts.
 public static void SandboxRegisterClientScriptBlock(string id, string url, Control control)
        {
            HtmlGenericControl script = new HtmlGenericControl("script");
            script.Attributes.Add("type", "text/javascript");
            script.InnerHtml = @"function wpLoad" + id + @"() {
                        if(document.getElementById('" + id + @"') == null)
                        {
                                   var script = document.createElement('script');
                                   script.type = 'text/javascript';
                                   script.id = '" + id + @"';
                                   script.src = '" + url + @"';
                                   document.body.appendChild(script);
                          }
                 }
                 _spBodyOnLoadFunctionNames.push('wpLoad" + id + @"');";
            control.Controls.Add(script);
        }
        public static void SandboxRegisterCss(string id, string url, Control control)
        {
            HtmlGenericControl css = new HtmlGenericControl("script");
            css.Attributes.Add("type", "text/javascript");
            css.InnerHtml = @"function wpLoad" + id + @"() {
                          if(document.getElementById('" + id + @"') == null) {
                                   var script = document.createElement('link');
                                   script.type = 'text/css';
                                   script.rel = 'stylesheet';
                                   script.id = '" + id + @"';
                                   script.href = '" + url + @"';
                                   document.body.appendChild(script);
                          }
                 }
                 _spBodyOnLoadFunctionNames.push('wpLoad" + id + @"');";
            control.Controls.Add(css);
        }