GridView排序问题，

我现在想在gridview里进行排序， if (!IsPostBack)
        {
            
            this.btnExport.Visible = false;
            ViewState["SortOrder"] ="Sno";
            ViewState["OrderDire"] ="ASC";
            ddlYearBind();
            gdvYearBind();        }
public void gdvYearBind()
    {
        SqlConnection con = db.GetConnection();
        con.Open();
        SqlDataAdapter sda = new SqlDataAdapter("proState",con);
        sda.SelectCommand.CommandType = CommandType.StoredProcedure;
        SqlParameter prams = new SqlParameter("@Term",SqlDbType.VarChar,20);
        prams.Value = this.ddlYear.SelectedValue;
        sda.SelectCommand.Parameters.Add(prams);
        DataSet ds = new DataSet();
        sda.Fill(ds,"table"); 
        DataView dv=ds.Tables["table"].DefaultView;     
        string sort = (string)ViewState["SortOrder"] + " " + (string)ViewState["OrderDire"];
        dv.Sort=sort; 
        gdvYear.DataSource=dv;
        gdvYear.DataBind();
        
    }
    protected void gdvYear_Sorting(object sender, GridViewSortEventArgs e)
    {
        string sPage = e.SortExpression; //设置进行排序的表达式
        if (ViewState["SortOrder"].ToString() == sPage)
        {            if (ViewState["OrderDire"].ToString() == "Desc")
                ViewState["OrderDire"] = "ASC";
            else
                ViewState["OrderDire"] = "Desc";
        }
        else
        {
            ViewState["SortOrder"] = e.SortExpression;
        }        gdvYearBind();
    }
这是我的代码，在运行的时候提示找不到列Sno，这是怎么回事啊?