聊天室AJAx读取消息

  读取消息：登录后读取登录后的消息，在首次获取消息的时候，得到最后一行的ID再次读消息的时候SQL语句去判断>最后行ID的值…….

登录后获取消息:

在页面创建

<asp:HiddenField ID="DATEnow" runat="server" />

if(!IsPostBack)
       {
           DATEnow.Value= DateTime.Now.ToString(); 首次运行创建登录时间赋值给DATEnow; 
      }

select f.Name as 'Formusername',t.Name as 'ToUsername',m.id,m.Fromuserid,m.TouserId,m.Message,m.recordTime,m.messageState,m.readflag from Message as m inner join Users as f on f.Id=m.FromUserId inner join Users as t on t.Id=m.ToUserId where m.recordtime>@getNowdate

<asp:HiddenField ID="lengthid" runat="server" />

WEBserver 中返回最后行的MSgs[MSgs.Count - 1].Id.ToString() 在js中得到var valueID=result[result.length-1].substring(result[result.length-1].lastIndexOf(',')+1)

再赋值给  document.getElementById("lengthid").value=valueID;

页面获取消息；

页面JS代码： 

  function $(j){return document.getElementById(j);}
       function GetObjectListCallBacks(result)
        {
          if(result.length!=0){
         for(var i=0;i<result.length;i++)
         {
           var valuesss=  result[i];
           var Hed=$("lengthid").value; 

           var valuess=  result[i].substring(0, result[i].lastIndexOf(',')); //这里是我返回值中最后面加了个ID用截取 ‘，’前的内容  就消息 

           var valueID=result[result.length-1].substring(result[result.length-1].lastIndexOf(',')+1);///这里得到的是ID
           $("lengthid").value=valueID;
           //$("Lid").value=valueID;测试最后个ID
           if(Hed<=valueID)
           {
               var newFontElem = document.createElement("font");
               newFontElem.innerHTML =valuess+"<br/>"
               $("Chat").appendChild(newFontElem);
               $("Chat").scrollTop= $("Chat").scrollHeight;//每次收到消息吧滚动条拉到最下面
           }
        }
        }
        }
        function getSTrijng()
        {
        var YY=$("lengthid").value;

        var XX =$("DATEnow").value; 

       JS.getKMSg(XX,YY,GetObjectListCallBacks); 

        setTimeout('getSTrijng()', 1000);
        }

页面代码：

<form id="form1" runat="server">
  <div>
      <asp:HiddenField ID="DATEnow" runat="server" />
      <asp:HiddenField ID="lengthid" runat="server" />
      <input type="text" id="Lid" />
      <div id="Chat">
      </div>
  </div>
  <asp:ScriptManager ID="ScriptManager1" runat="server">
      <Services>
          <asp:ServiceReference Path="JS.asmx" /> 
      </Services>
  </asp:ScriptManager>
  </form>

WEBserver代码：

在wenserver 中加

[System.Web.Script.Services.ScriptService] //必须加上这句 不然JS会无法找到的
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class JS : System.Web.Services.WebService
{

    public JS()
    {

        //如果使用设计的组件，请取消注释以下行
        //InitializeComponent();
    }
    [WebMethod]
    public List<String> getKMSg(String XX, String YY)
    {
        if (YY != "") //这个是没有最后个ID的时候执行的BLL层的东东
        {
            List<string> listStr = new List<string>();
            StringBuilder geTMsglist = new StringBuilder();
            List<Message> MSgs = new List<Message>();
            MSgs = new BLL.MsgCtergor().readMSg(5, 9999, DateTime.Parse(XX), int.Parse(YY.ToString()));//关键语句再上面已经说出
            if (MSgs.Count > 0)
            {
                for (int i = 0; i < MSgs.Count; i++)
                {
                    String formname = MSgs[i].Formusername.ToString();
                    String Toname = MSgs[i].ToUsername.ToString();
                    String SEnddate = MSgs[i].RecordTime.ToString();
                    String Sendtext = "  " + formname + "对" + Toname + "说[" + SEnddate + "]<br />";
                    String tEXS = MSgs[i].Messag.ToString();
                    Sendtext += "<B>" + tEXS + "</B>," + MSgs[MSgs.Count - 1].Id.ToString() + "";
                    geTMsglist.Append(Sendtext);
                    listStr.Add(geTMsglist.ToString());
                }
            }
            return listStr;
        }
        else
        {

        //这个是首次登录后的消息
            List<string> listStr = new List<string>();
            StringBuilder geTMsglist = new StringBuilder();
            List<Message> MSgs = new List<Message>();
            MSgs = new BLL.MsgCtergor().readMSg(0, 9999, DateTime.Parse(XX), 9999);//关键语句再上面已经说出
            if (MSgs.Count > 0)
            {
                for (int i = 0; i < MSgs.Count; i++)
                {
                    String formname = MSgs[i].Formusername.ToString();
                    String Toname = MSgs[i].ToUsername.ToString();
                    String SEnddate = MSgs[i].RecordTime.ToString();
                    String Sendtext = "  " + formname + "对" + Toname + "说[" + SEnddate + "]<br />";
                    String tEXS = MSgs[i].Messag.ToString();
                    Sendtext += "<B>" + tEXS + "</B>," + MSgs[MSgs.Count - 1].Id.ToString() + "";
                    geTMsglist.Append(Sendtext);
                    listStr.Add(geTMsglist.ToString());
                }

            }
            return listStr;
        }
    }

}