发送按钮不会使用SignalR聊天将预期消息推送到SQL数据库中

Question

<form id ="form1" runat="server">
            <asp:ScriptManager EnablePartialRendering="true" ID="ScriptManager1" runat="server"></asp:ScriptManager>
            <div>


            <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">

                <ContentTemplate>

                    <asp:TextBox ID="message" runat="server"></asp:TextBox>
                    <asp:Button ID="sendmessage" runat="server" Text="send" OnClick="sendmessage_Click" />

                    <input type="hidden" id="displayname" value="<%= buyer %>" />

                </ContentTemplate>
            </asp:UpdatePanel>

            <!-- dISPLAY messages -->   
            <ul id="discussion">
                <% if (chatList != null) {  %>
                    <% foreach (var item in chatList) { %>
                        <li><strong><%=item.buyer %> : </strong></li> <%= item.msg %>
                    <% }  %>
                <% } else { %>
                    <li><strong>No chat</strong></li>
                <% }  %>
            </ul>


            <%--<asp:UpdatePanel ID="UpdatePanel2" runat="server" UpdateMode="Conditional">
                <ContentTemplate>
                    <asp:Label ID="Label2" runat="server" ForeColor="red" />
                </ContentTemplate>
                <Triggers>
                    <asp:AsyncPostBackTrigger ControlID="Button1" EventName="Click" />
                </Triggers>
            </asp:UpdatePanel>--%>


            </div>
        </form>

<!-- javascript -->
$(function () {
            ....
            // Create a function that the hub can call to broadcast messages.
            chat.client.broadcastMessage = function (<%= buyer %>, message) {
                // Html encode display name and message. 
                console.log("appended");
                var encodedName = $('<div />').text(<%= buyer %>).html();
                var encodedMsg = $('<div />').text(message).html();

                // Add the message to the page. 
                $('#discussion').append('<li><strong>' + encodedName
                    + '</strong>:&nbsp;&nbsp;' + encodedMsg + '</li>');
            };

           .....

            // start connection
            $.connection.hub.start().done(function () {
                $('#<%=sendmessage.ClientID %>').click(function() {
                    // Call the Send method on the hub. 
                    console.log("CLicked");
                    chat.server.send($('#displayname').val(), $('#<%=message.ClientID%>').val());
                    console.log($('#<%=message.ClientID%>').val());
                    // Clear text box and reset focus for next comment. 
                    $('#<%=message.ClientID%>').val('').focus();
                });
            });
        });

     <!-- Server side to push messages into SQL database -->
     protected void sendmessage_Click(object sender, EventArgs e)
    {
        itemid = Request.QueryString["itemid"];
        buyer = Request.QueryString["buyer"];
        seller = Request.QueryString["seller"];
        item = Request.QueryString["item"];
        time = DateTime.Now.ToString("HH:mm:ss");
        date = DateTime.Today.ToString("dd-MM-yyyy");
        msg = message.Text;
        productDAO productdao = new productDAO();
        productdao.push(buyer, msg, Convert.ToInt32(itemid), seller, time, date, item);
    }

第一次单击发送按钮时，消息将显示在ul标签中，该ul标签用于显示消息。但是，从第二次开始，情况恰恰相反。消息被推送到数据库中，但是消息未显示在ul标记中。我已经尝试过在线使用AJAX和其他解决方案，但似乎没有任何效果。我可以知道我的代码出了什么问题吗？