问题：
Datalist1显示say这个表的数据 
然后想在Datalist1中嵌套一个Datalist2用于显示对应的评论 
表2的 sayID对应表1的id，若表2中找不到对应sayId则在对应的Datalist1中不显示Datalist2.
难点在于如何达到“林夏”的说说下面只显示“黄磊”、“叶伟信”的评论，“韩寒”的下面只显示“程程”的评论。（林夏的id是3，所以查询对应的表2中sayId为3的行）。
代码
前台代码：
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
<link href="Content/bootstrap.css" rel="stylesheet" />
</head>
<body>
<form id="form1" runat="server">
<h2 style="text-align:center;">评论列表</h2>
<div align="center" style="margin-top:20px;">
<asp:DataList ID="DataList1" runat="server" OnItemDataBound="DataList1_ItemDataBound" Width="50%" CssClass="table table-bordered"
CellPadding="0" CellSpacing="0">
<ItemTemplate>
<div>
来自<%# Eval("place") %>的<%# Eval("username") %>于<%# Eval("date") %>发表
</div>
<div>
<%# Eval("text") %>
</div>
<asp:DataList ID="DataList2" runat="server" Width="100%">
<ItemTemplate>
<div style="border: 1px dashed black; margin: 1px;">
<div>
<%#Eval("username") %>的评论<%#Eval("date") %>
</div>
<div>评论内容：<%#Eval("text") %> </div>
</div>
</ItemTemplate>
</asp:DataList>
</ItemTemplate>
</asp:DataList>
</div>
</form>
</body>
</html>后台cs：
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
this.DataList1.DataSource = Data();
this.DataList1.DataBind();
}
}
public DataSet Data()
{
DataSet ds = new DataSet();
DataTable dtParent = new DataTable();
dtParent.Columns.Add("id", typeof(int));
dtParent.Columns.Add("username", typeof(string));
dtParent.Columns.Add("text", typeof(string));
dtParent.Columns.Add("date", typeof(string));
dtParent.Columns.Add("place", typeof(string));
dtParent.Rows.Add(1, "摩根", "这个...", "2014.6", "伦敦");
dtParent.Rows.Add(2, "韩寒", "潮流...", "2015.7", "湖南");
dtParent.Rows.Add(3, "林夏", "岁月...", "2016.2", "小城");
dtParent.Rows.Add(4, "王菲", "我会...", "2015.9", "香港");
dtParent.Rows.Add(5, "郭敬明", "我们...", "2015.1", "上海");
DataTable dtChild = new DataTable();
dtChild.Columns.Add("id", typeof(int));
dtChild.Columns.Add("sayId", typeof(int));
dtChild.Columns.Add("username", typeof(string));
dtChild.Columns.Add("text", typeof(string));
dtChild.Columns.Add("date", typeof(string));
dtChild.Rows.Add(1, 3, "黄磊", "我是第一个评说", "2016.6.17 13:06:12");
dtChild.Rows.Add(3, 3, "叶伟信", "评论林夏的说", "2016.6.17 12:26:43");
dtChild.Rows.Add(4, 2, "程程", "我评论韩寒", "2015.3.1 15:20:10");
ds.Tables.AddRange(new DataTable[] { dtParent, dtChild });
DataRelation dr = new DataRelation("relation", dtParent.Columns["id"], dtChild.Columns["sayId"]);
ds.Relations.Add(dr);
dtParent = ds.Relations["relation"].ParentTable;
dtChild = ds.Relations["relation"].ChildTable;
return ds;
}
protected void DataList1_ItemDataBound(object sender, DataListItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
DataList dataList = e.Item.FindControl("DataList2") as DataList;
DataRowView rowv = (DataRowView)e.Item.DataItem;
DataRow[] rows = Data().Tables[1].Select("sayId='" + rowv["id"].ToString() + "'");
DataTable dt = Data().Tables[1].Clone();
foreach (DataRow dr in rows)
{
dt.ImportRow(dr);
}
dataList.DataSource = dt;
dataList.DataBind();
}
}后台代码中数据源部分可以用ado.net查询数据库方式替换。
效果图：
