局部内容添加

//前台代码

    <div id="commentContainer">
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <asp:Repeater ID="Repeater1" runat="server">
                    <ItemTemplate>
                        <%# (Container.DataItem as Comment).Content %><br />
                        <i><%# (Container.DataItem as Comment).Time %></i>
                        <hr />
                    </ItemTemplate>
                </asp:Repeater>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="Button1" />
            </Triggers>
        </asp:UpdatePanel>
    </div>
    
    <br />
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox><br />
    <asp:Button ID="Button1" runat="server" Text="Add Comment" OnClick="Button1_Click" />

    <script language="javascript" type="text/javascript">
        Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(
            function(sender, e)
            {
                var upId = "<%= this.UpdatePanel1.ClientID %>";
                var refreshedPanels = e.get_panelsUpdated();
                
                for (var i = 0; i < refreshedPanels.length; i++)
                {
                    if (refreshedPanels[i].id == upId)
                    {
                        refreshedPanels[i].id = upId + Math.floor(9999 * Math.random());
                        var div = document.createElement("div");
                        div.id = upId;
                        $get("commentContainer").appendChild(div);
                        return;
                    }
                }
            });
    </script>

//后台代码

    private static List<Comment> Comments;
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            // 在第一次打开页面时清空所有Comments。
            // 古怪的用法，仅在这个示例时这么用。
            Comments = new List<Comment>();
            this.BindComments();
        }
    }

    private void BindComments()
    {
        this.Repeater1.DataSource = Comments;
        this.Repeater1.DataBind();
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        Comment comment = new Comment();
        comment.Content = this.TextBox1.Text;
        comment.Time = DateTime.Now;

        // Comments.Add(comment);
        this.Repeater1.DataSource = new Comment[] { comment };
        // this.BindComments();
        this.Repeater1.DataBind();
    }

//实体类

public class Comment
{
    public string Content;

    public DateTime Time;
}