突然发现这个问题：
xxx.aspx
<asp:Repeater ID="Repeater1" runat="server" DataSourceID="SqlDataSource1" OnItemCommand="Repeater1_ItemCommand">
        <ItemTemplate><%# Eval("categoryname") %>[<asp:LinkButton ID="lnk" CommandName="Select" Text="DropComment" runat="server"></asp:LinkButton>]</ItemTemplate>
        </asp:Repeater>
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:DefaultConnectionstrings %>"
            SelectCommand="SELECT * FROM [Category]"></asp:SqlDataSource>

已经声明了OnItemCommand事件，.cs中
 protected void Repeater1_ItemCommand(object source, RepeaterCommandEventArgs e)
    {
        Response.Write(e.CommandName);
    }
运行，点击DropComment，并没有显示e.CommandName的值。

去掉Repeater的DataSourceID属性，在.cs中对Repeater进行数据绑定：
 protected void Page_Load(object sender, EventArgs e)
    {
      
            using (SqlConnection conn = new SqlConnection(global.ConnectionString))
            {
                SqlCommand comm = new SqlCommand("SELECT * FROM [Category]", conn);
                conn.Open();
                this.Repeater1.DataSource = comm.ExecuteReader(CommandBehavior.CloseConnection);
                this.Repeater1.DataBind();
            }
       
    }
再运行，点击DropComment，显示"DropComment"，说明触发了OnItemCommand事件。
疑问了，为什么用数据源控件时无法触发OnItemCommand事件了？