新手求助！！急急急

using System;
using System.Data;
using System.Data.SqlClient;
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;

public partial class _Default : System.Web.UI.Page
{
    string strconn = "data source=localhost://SQLEXPRESS;initial catalog=Northwind;user id=sa;password=sa123";
    SqlConnection myconn = new SqlConnection(strconn);

    protected void Page_Load(object sender, EventArgs e)
    {
      
        string strSQL = "select top 5 CategoryID,CategoryName,Description from Categories";
        SqlCommand mycomm = new SqlCommand(strSQL, myconn);
        myconn.open();
        mygv.DataSource = myCommand.ExecuteReader();
        mygv.DataBind();
        myconn.close();
    }
}
显示System.Data.SqlClint 不包含open 和  close的定义  
各位大虾帮帮忙

应该是大写的Open和Close方法，c#是区分大小写的

谢谢，我太粗心了！谢谢