GridView排序

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.Data.SqlClient;

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            bindGridView();
        }
    }

    private void bindGridView()
    {
        SqlConnection sqlcon = new SqlConnection(@"Data Source=PC-20100627ZYHG;Initial Catalog=peter;Integrated Security=True");
        sqlcon.Open();
        SqlDataAdapter sqlAd=new SqlDataAdapter("select * from Student",sqlcon);
        DataSet ds=new DataSet();
        sqlAd.Fill(ds,"student");
        sqlcon.Close();
        this.GridView1.DataSource=ds;
        this.GridView1.DataBind();
    }
    protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
    {        
        DataControlField clm = null;

        for (int i = 0; i < this.GridView1.Columns.Count; i++)
        {
            if (this.GridView1.Columns[i].SortExpression == e.SortExpression)
            {
                clm = this.GridView1.Columns[i];
                break;
            }
        }
        if (clm == null) return;
        if (e.SortExpression.ToLower().IndexOf("desc") > 0)
        {
            clm.SortExpression = e.SortExpression.ToLower().Replace("desc", "asc");
        }
        else
        {
            if (e.SortExpression.ToLower().IndexOf("asc") > 0)
            {
                clm.SortExpression = e.SortExpression.ToLower().Replace("asc", "desc");
            }
            else
            {
                clm.SortExpression = e.SortExpression.ToLower() + " desc";
            }
        }

        this.bindGridView(clm.SortExpression);
    }

    private void bindGridView(string strSort)
    {
        SqlConnection sqlcon = new SqlConnection(@"Data Source=PC-20100627ZYHG;Initial Catalog=peter;Integrated Security=True");
        sqlcon.Open();
        SqlDataAdapter sqlAd = new SqlDataAdapter("select * from Student", sqlcon);
        DataSet ds = new DataSet();
        sqlAd.Fill(ds, "student");
        sqlcon.Close();
        ds.Tables[0].DefaultView.Sort = strSort;
        this.GridView1.DataSource = ds.Tables[0].DefaultView;
        this.GridView1.DataBind();
    }
}