书籍父类别和子类别的显示

原理：前台两个 DataList 的嵌套

<!-- 放置DataList数据控件  -->
         <asp:DataList ID="ParentCaption" runat="server" RepeatDirection="Vertical" onitemdatabound="ParentCaption_ItemDataBound">
         <ItemTemplate>
           <div style=" height:20px; width:185px; background-color:#f0f0f0;font-weight:bold; ">
             [&nbsp;<%# Eval("Type_Name")%>&nbsp;]
           </div>           
           
          <!-- 子标题  -->   
          <asp:DataList ID="SonCaption" runat="server" RepeatDirection="Horizontal" RepeatColumns="2">
          <ItemTemplate>
            <div style="margin-left:20px; list-style-type:none;">
              <a href='<%# "SortBooks.aspx?TypeID="+Eval("Type_ID") %> '>
                  <asp:Label ID="Label1" runat="server" Text='<%# Eval("Type_Name")%> '></asp:Label> </a>
            </div>      
           </ItemTemplate>
          </asp:DataList>
         </ItemTemplate>
        </asp:DataList>
<!-- 放置DataList数据控件  -->  

后台对两个 DataList 进行绑定：
   protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            bindParentType();
        }
    }

    private void bindParentType()
    {
        DataSet ds = new DataSet();
        if (this.Cache["Type_Name"] == null)
        {
            BLL.BookCategory bookType = new BLL.BookCategory();
            ds = bookType.GetList("");
            this.Cache.Insert("Type_Name", ds, null, DateTime.Now.AddMinutes(10), TimeSpan.Zero);
        }
        else
        {
            ds = (DataSet)this.Cache["Type_Name"];
        }
        DataRow[] darow = ds.Tables[0].Select(" Type_FatherTypeID is null");
        DataTable dt = ds.Tables[0].Clone();
        foreach (DataRow dr in darow)
        {
            dt.ImportRow(dr);
        }
        this.ParentCaption.DataSource = dt;
        this.ParentCaption.DataKeyField = "Type_ID";
        this.ParentCaption.DataBind();
    }

    //在父级 DataList 内找子级 DataList 控件
    protected void ParentCaption_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        DataList dl2 = (DataList)e.Item.FindControl("SonCaption");
        int parentID = Convert.ToInt32(this.ParentCaption.DataKeys[e.Item.ItemIndex].ToString());

        DataSet ds = (DataSet)this.Cache["Type_Name"];
        DataRow[] dro = ds.Tables[0].Select(" Type_FatherTypeID=" + parentID);
        DataTable dt = ds.Tables[0].Clone();
        foreach (DataRow dr in dro)
        {
            dt.ImportRow(dr);
        }
        dl2.DataSource = dt;
        dl2.DataBind();
    }