GridView中实现双向排序

1.aspx前台代码

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" AllowSorting="true" OnSorting="GridView1_Sorting" AllowPaging="true" PageSize="10" OnPageIndexChanging="GridView1_PageIndexChanging">
                        <Columns>
                        <asp:BoundField DataField="deptid" HeaderText="部门代码" SortExpression="deptid"/>
                        <asp:BoundField DataField="deptename" HeaderText="部门名称" SortExpression="deptename"/>
                        <asp:TemplateField SortExpression="BUID" HeaderText="BUID">
                        <ItemTemplate>
                            <asp:Label ID="Label1" runat="server"   Text='<%# Bind("BUID") %>' ToolTip='<%# DataBinder.Eval(Container.DataItem, "BUID") %>'></asp:Label>
                        </ItemTemplate>
                        </asp:TemplateField>
                        </Columns>
                        </asp:GridView>

2.aspx.cs后台代码

protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            ViewState["SortOrder"] = "deptid";
            ViewState["OrderDire"] = "asc";
            BindGridView();
        }
    }

    protected void BindGridView()
    {
      
        DataSet ds = new DataSet();
        ds = MIS.Users.GetDept();

        DataView dv = ds.Tables[0].DefaultView;
        string sort = (string)ViewState["SortOrder"] + " " + (string)ViewState["OrderDire"];
        dv.Sort = sort;

        this.GridView1.DataSource = dv;

        this.GridView1.DataBind();

    }
    protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
    {
        string vortExp = e.SortExpression;
        if (ViewState["SortOrder"].ToString() == vortExp)
        {
            if ((string)ViewState["OrderDire"] == "desc")
            {
                ViewState["OrderDire"] = "asc";
            }
            else if ((string)ViewState["OrderDire"] == "asc")
            {
                ViewState["OrderDire"] = "desc";
            }
        }
        else
        {
            ViewState["SortOrder"] = e.SortExpression;
        }
        BindGridView();

    }
    protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        this.GridView1.PageIndex = e.NewPageIndex;
        BindGridView();
    }