再问！自定义控件问题

Question

写了自定义控件，也给相应的网站项目添加了引用，但是从工具箱面板上把该自定义控件拖到页面时说：
呈现控件时出错初始化字符串格式不符合规范，是哪里错误了呢？

Answer 1

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.OleDb;
using System.Data;
using System.Xml;namespace WebControlLibrary1
{
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:WebCustomControl1 runat=server></{0}:WebCustomControl1>")]
    public class showAd : WebControl
    {
        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string Text
        {
            get
            {
                String s = (String)ViewState["Text"];
                return ((s == null) ? String.Empty : s);
            }            set
            {
                ViewState["Text"] = value;
            }
        }
        [Bindable(true)]
        [Category("appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string type
        {
            get
            {
                String s = (String)ViewState["type"];
                return ((s == null) ? String.Empty : s);
            }
            set
            {
                ViewState["type"] = value;
            }
        }        [Bindable(true)]
        [Category("appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string adid
        {
            get
            {
                String s = (String)ViewState["adid"];
                return ((s == null) ? String.Empty : s);
            }
            set
            {
                ViewState["adid"] = value;
            }
        }        [Bindable(true)]
        [Category("appearance")]
        [DefaultValue("~/App_Data/maikou.mdb")]
        [Localizable(true)]
        public string dbpath
        {
            get
            {
                String s = (String)ViewState["dbpath"];
                return ((s == null) ? String.Empty : s);
            }
            set
            {
                ViewState["dbpath"] = value;
            }
        }        [Bindable(true)]
        [Category("appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public String showNum
        {
            get
            {
                String s = (String)ViewState["shownum"];
                return ((s == null) ? String.Empty : s);
            }
            set
            {
                ViewState["shownum"] = value;
            }
        }        [Bindable(true)]
        [Category("appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string cssStyle
        {
            get
            {
                String s = (String)ViewState["cssStyle"];
                return ((s == null) ? String.Empty : s);
            }
            set
            {
                ViewState["cssStyle"] = value;
            }
        }        protected override void RenderContents(HtmlTextWriter output)
        {
            string connstr = MapPathSecure("~/App_Data/maikou.mdb");
            if (dbpath != null)
            {
                connstr = dbpath;
            }            OleDbConnection conn = new OleDbConnection(connstr);
            conn.Open();            string sql;
            if (type != null && adid != null)
            {
                sql = "select * from ads where types='" + type + "' and id='" + adid + "' order by id desc";
            }
            else if (type != null)
            {
                sql = "select * from ads where types='" + type + "' order by id desc";
            }
            else if (adid != null)
            {
                sql = "select * from ads where id='" + adid + "' order by id desc";
            }
            else
            {
                sql = "select * from ads order by id desc";
            }            OleDbDataAdapter oda = new OleDbDataAdapter(sql, conn);
            DataSet ds = new DataSet();
            int count = oda.Fill(ds, "adtable");
            DataTable thistable = ds.Tables["adtable"];
            if (count > 0)
            {
                if (count > Convert.ToInt32(showNum))
                {
                    count = Convert.ToInt32(showNum);
                    StringBuilder build = new StringBuilder();
                    build.Append("<div style=\"border:1px solid #ffcc99;\">");
                    for (int i = 0; i < count; i++)
                    {
                        build.Append("<div style=\"border:1px dashed #cccccc;\"><a href=\"" + thistable.Rows[i]["url"].ToString() + "\" target=\"black\">" + thistable.Rows[i]["name"].ToString() + "</a></div>");
                    }
                    build.Append("</div>");
                    Text = build.ToString();
                }
            }
            else
            {
                Text = "暂时没有数据";
            }            output.Write(Text);        }
    }
}