SQL2005问题

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

public partial class _vote : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(@"Data Source=localhost\SQLEXPRESS; database=select; uid=sa;pwd=;");
        con.Open();
        //查询选举的标题
        SqlCommand cmd=new SqlCommand ("select vo_title from vote where vo_id="+this.vo_id,con);
        string title = Convert.ToString(cmd.ExecuteScalar());
        this.Label1.Text = title;
        //查询对应的投票条目
        SqlCommand cmdItem = new SqlCommand("select vo_Item,vo_id from votedetails where vo_id=" + this.vo_id, con);
        SqlDataReader sdr = cmdItem.ExecuteReader();
        this.rdblist.DataSource = sdr;
        this.rdblist.DataTextField = "vo_title";
        this.rdblist.DataValueField = "vo_id";
        this.rdblist.DataBind();
        sdr.Close();
        con.Close();
    }
}
在运行上面这段代码时，出现“_vote”并不包含“vo_id”的定义
在表vote和votedetails中创建了vo_id这个字段，为什么还会出现 这样的字段，这是怎么回事，该怎样解决？