Problem with implement interface

<pre>
using System;
using HtmlAgilityPack;
using System.Linq;
using System.Collections.Generic;

namespace Project1.CommonLayer.PublicClass
{

    public class SearchModel :ISearchModel
    {



        private string _resultread;
        public SearchModel(string _url)

        {
            _resultread = _url;

             readurl(_resultread);

        }





        public class _UrlList
        {
            public int UrlNumber { get; set; }
            public string UrlDesc { get; set; }
            public int LineNumber { get; set; }


        }


        public List<_UrlList>  readurl (string inputString)
        {


          Return list;



            }