利用模板列实现DataGrid控件的双向排序

    初用DataGrid控件，想实现点击表头来对数据进行双向排序，费了老半天工夫才摸索出如下的东东来，请看效果图：  
   

DataGrid设置如下：

<asp:DataGrid id="faggruppeGrid" runat="server" BorderColor="Black" BorderWidth="1px" CellPadding="3"
    Width="300px" HeaderStyle-BackColor="#7f9db9" HorizontalAlign="Center" AutoGenerateColumns="False"
    AllowSorting="True">
    <HeaderStyle BackColor="#7F9DB9"></HeaderStyle>
    <Columns>
    <!-- 第一列 -->
     <asp:TemplateColumn>
      <HeaderTemplate>
       <asp:LinkButton id="lbFag" runat="server" CommandName="sort" CommandArgument="Fag" CausesValidation="False">Fag</asp:LinkButton>
       <asp:Image Runat="server" ID="ImgFag" ImageUrl="../images/Up.gif" Visible="False" />    <!--箭头图标-->
      </HeaderTemplate>
      <ItemTemplate>
       <asp:Label runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Fag") %>' ID="Label1"/>
      </ItemTemplate>
     </asp:TemplateColumn>
    <!-- 第二列 -->
     <asp:TemplateColumn>
      <HeaderTemplate>
       <asp:LinkButton id="lbNavn" runat="server" CommandName="sort" CommandArgument="Navn" CausesValidation="False">Navn</asp:LinkButton>
       <asp:Image Runat="server" ID="ImgNavn" ImageUrl="../images/Up.gif" Visible="False" />
      </HeaderTemplate>
      <ItemTemplate>
       <asp:Label runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Navn") %>' ID="Label2"/>
      </ItemTemplate>
     </asp:TemplateColumn>
    <!-- 第三列 -->
     <asp:HyperLinkColumn DataNavigateUrlField="Fag" DataNavigateUrlFormatString="JavaScript:ReturnFagnummer('{0}');" Text="Indsæt" />
    </Columns>
   </asp:DataGrid>

后台处理代码：

 

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using Pensam.Praesentation.BMSWIService;
using Pensam.GenNS;
using Microsoft.ApplicationBlocks.ExceptionManagement;

namespace Pensam.Praesentation.Medarbejder
{
    /**//// <summary>
    /// Summary description for FaggruppeListe.
    /// </summary>
    public class FaggruppeListe : BaseWebPage
    {
        member variables#region member variables
        protected System.Web.UI.WebControls.DataGrid faggruppeGrid;
        protected System.Web.UI.WebControls.Image ImgArrow = null;
        private DataTable dt = null;
        #endregion

        private void Page_Load(object sender, System.EventArgs e)
        {
            VisFagGrps();
            if(!this.IsPostBack) BindGrid();
            //if(this.IsPostBack) Response.Write("post back");
        }

        Web Form Designer generated code#region Web Form Designer generated code
        override protected void OnInit(EventArgs e)
        {
            //
            // CODEGEN: This call is required by the ASP.NET Web Form Designer.
            //
            InitializeComponent();
            base.OnInit(e);
        }
        
        /**//// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {    
            this.faggruppeGrid.SortCommand += new System.Web.UI.WebControls.DataGridSortCommandEventHandler(this.faggruppeGrid_SortCommand);
            this.faggruppeGrid.ItemDataBound += new System.Web.UI.WebControls.DataGridItemEventHandler(this.faggruppeGrid_ItemDataBound);
            this.Load += new System.EventHandler(this.Page_Load);

        }
        #endregion

        private functions#region private functions
        //生成绑定数据
        private void VisFagGrps()
        {
            /**//*
            using(PSLog logger = new PSLog())
            {
                try
                {
                    if(this.ServiceDelegate == null) return;
                    ArrayList list1 = new ArrayList(this.ServiceDelegate.GetFaggruppeListe());
                    if(list1 == null)
                    {
                        this.VisErrorMessage("Get professional category list failed.");
                    }
                }
                catch(Exception ex)
                {
                    VisErrorMessage(ex.Message);
                    ExceptionManager.Publish(ex);
                }
            }
            */
            

            dt = new DataTable();
            DataRow dr;

            dt.Columns.Add(new DataColumn("Fag", typeof(string)));
            dt.Columns.Add(new DataColumn("Navn", typeof(string)));

            dr = dt.NewRow();
            dr["Fag"] = "Fag01000001";
            dr["Navn"] = "Fag0101";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Fag"] = "Fag01000002";
            dr["Navn"] = "Fag0102";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Fag"] = "Fag01000003";
            dr["Navn"] = "Fag0103";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Fag"] = "Fag02000001";
            dr["Navn"] = "Fag0201";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Fag"] = "Fag02000002";
            dr["Navn"] = "Fag0202";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Fag"] = "Fag02000003";
            dr["Navn"] = "Fag0203";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Fag"] = "Fag03000001";
            dr["Navn"] = "Fag0301";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Fag"] = "Fag03000002";
            dr["Navn"] = "Fag0302";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Fag"] = "Fag03000003";
            dr["Navn"] = "Fag0303";
            dt.Rows.Add(dr);
        }

        private void faggruppeGrid_SortCommand(Object sender, DataGridSortCommandEventArgs e) 
        {
            System.Web.UI.Control control = ((DataGridItem)e.CommandSource).FindControl("ImgArrow");
            //Response.Write(control.ToString());
            ImgArrow = (System.Web.UI.WebControls.Image)control;
            string SortField = (string)e.SortExpression;
            string oldSortParam = faggruppeGrid.Attributes["SortExpression"];
            if(oldSortParam.StartsWith(SortField))
            {
                //order by the same column.
                 if(oldSortParam.EndsWith("ASC")) 
                    {
                         oldSortParam = oldSortParam.Replace("ASC","DESC");
                         //ImgArrow.ImageUrl = "../Images/Up.gif"; //实践证明在此设置图像行不通,需在ItemDataBound事件中实现。
                    }
                    else
                    {
                        oldSortParam = oldSortParam.Replace("DESC","ASC");
                        //ImgArrow.ImageUrl = "../Images/Up.gif"; //实践证明在此设置图像行不通，需在ItemDataBound事件中实现。
                    }

            }
            else
            {
                oldSortParam = SortField + " ASC";
            }
            faggruppeGrid.Attributes["SortExpression"] = oldSortParam;
            BindGrid();
        }

        //绑定数据
        private void BindGrid()
        {
            //设置初始排序字段
            if(faggruppeGrid.Attributes["SortExpression"] == null)
                faggruppeGrid.Attributes["SortExpression"] = "Fag ASC";
            DataView dv = dt.DefaultView;
            //按指定的排序字段排序
            dv.Sort = faggruppeGrid.Attributes["SortExpression"];
            faggruppeGrid.DataSource = dt;
            faggruppeGrid.DataBind();
        }

        private void faggruppeGrid_ItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
        {
            if(e.Item.ItemType != ListItemType.Header) return;
            //以下获取排序表达式
            if(faggruppeGrid.Attributes["SortExpression"]==null) return;
            string sortExpression = faggruppeGrid.Attributes["SortExpression"];
            string[] orderParams = sortExpression.Split(' ');
             //获取Image对象
            System.Web.UI.Control control = (e.Item).FindControl("Img" + orderParams[0]);

            if(control == null) return;
            ImgArrow = (System.Web.UI.WebControls.Image)control;
            ImgArrow.Visible = true;

            //设置图像Url
            if(sortExpression.EndsWith("ASC")) 
                ImgArrow.ImageUrl = "../Images/Up.gif";
            else
                ImgArrow.ImageUrl = "../Images/Down.gif";
        }

        #endregion
    }
}