GridView扩展--自动排序

 public class GridViewEX:GridView
    {

        public delegate void BindEventHandler();

        DataSet _ds;
        [Description("自定义的DataSet类型数据源"), Category("扩展")]
        public virtual DataSet DataSetSource
        {
            get
            {
                return _ds;
            }
            set
            {
                _ds = value;
            }
        }

        public event BindEventHandler Bind;
        public virtual void OnBind()
        {
            if (Bind != null)
            {
                Bind();
                if (DataSetSource != null)
                {
                    DataView dv = DataSetSource.Tables[0].DefaultView;
                    dv.Sort = SortExpressionStr;
                    this.DataSource = dv;

                    this.DataBind();
                }
            }
        }

        [Description("排序表达式"), Category("扩展")]
        protected virtual string SortExpressionStr
        {
            get
            {
                if (ViewState["SortExpression"] == null)
                {
                    return null;
                }
                return ViewState["SortExpression"].ToString();
            }
            set
            {
                ViewState["SortExpression"] = value;
            }
        }
        [Description("排序方向"), Category("扩展")]
        protected virtual string SortDirectionStr
        {
            get
            {
                if (ViewState["SortDirection"] == null)
                {
                    return "DESC";
                }
                if (ViewState["SortDirection"].ToString().ToLower() != "asc" && ViewState
          ["SortDirection"].ToString().ToLower() != "desc")
                {
                    return "DESC";
                }
                return ViewState["SortDirection"].ToString();
            }
            set
            {
                ViewState["SortDirection"] = value;
            }
        }

        public string SortExpressionEx
        {
            get
            {
                if (ViewState["SortExpressionEx"] == null)
                {
                    return null;
                }
                return ViewState["SortExpressionEx"].ToString();
            }
            set
            {
                ViewState["SortExpressionEx"] = value;
            }
        }

        protected override void OnSorting(GridViewSortEventArgs e)
        {
            SortExpressionEx = e.SortExpression;
            SortExpressionStr = e.SortExpression + " " + SortDirectionStr;
            OnBind();
            if (SortDirectionStr.ToLower() == "asc")
            {
                SortDirectionStr = "DESC";
            }
            else
            {
                SortDirectionStr = "ASC";
            }
        }

        protected override void OnLoad(EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                try
                {
                    OnBind();
                }
                catch
                {

                }
            }
            base.OnLoad(e);
        }

    }