Asp.net动态加载用户自定义控件,并转换成HTML代码

public static string RangerUsControl(string controlName)
        {
            StringBuilder build = new StringBuilder();
            HtmlTextWriter htmlWriter = new HtmlTextWriter(new StringWriter(build));
            UserControl uc = new UserControl();
            Control ctrl=uc.LoadControl(controlName+".ascx");//加载用户定义控件
            htmlWriter.Flush();
            string result;
            try 
            { 
                ctrl.RenderControl(htmlWriter);
            }
            catch { }
            finally 
            { 
                htmlWriter.Flush();
                result=build.ToString();
            }
            return result;//返回控件的HTML代码
        }