在AJAX中从ASHX获取数据javascript

Question

创建： 处理程序在数据库中检查是否有新的消息。

我到目前为止所做的： 使用AJAX的Javascript每三秒运行一次处理程序。

我无能为力：将结果从ASHX处理程序返回给AJAX javascript，以便在结果为true时执行回发。

这里是JavaScript的：

//handle message upload 

     window.setInterval(function() { 

      $.ajax({ 
       url: "handlecb.ashx", 
       type: "POST", 

       success: function (result) { 
        toastr.options = { 
         "closeButton": false, 
         "debug": false, 
         "newestOnTop": true, 
         "progressBar": false, 
         "positionClass": "toast-bottom-left", 
         "preventDuplicates": true, 
         "onclick": null, 
         "showDuration": "1300", 
         "hideDuration": "1300", 
         "timeOut": "5300", 
         "extendedTimeOut": "1000", 
         "showEasing": "swing", 
         "hideEasing": "linear", 
         "showMethod": "fadeIn", 
         "hideMethod": "fadeOut" 
        } 
        toastr.info('Online.'); 

        if (result < 0) { 
         __doPostBack("<%= senbut.ClientID %>", ""); 
         toastr.options = { 
          "closeButton": false, 
          "debug": false, 
          "newestOnTop": true, 
          "progressBar": false, 
          "positionClass": "toast-bottom-left", 
          "preventDuplicates": true, 
          "onclick": null, 
          "showDuration": "1300", 
          "hideDuration": "1300", 
          "timeOut": "5300", 
          "extendedTimeOut": "1000", 
          "showEasing": "swing", 
          "hideEasing": "linear", 
          "showMethod": "fadeIn", 
          "hideMethod": "fadeOut" 
         } 
         toastr.success('New message recieved.'); 
        } 


       }, 
       error: function (err) { 
        toastr.options = { 
         "closeButton": false, 
         "debug": false, 
         "newestOnTop": true, 
         "progressBar": false, 
         "positionClass": "toast-bottom-left", 
         "preventDuplicates": true, 
         "onclick": null, 
         "showDuration": "1300", 
         "hideDuration": "1300", 
         "timeOut": "5300", 
         "extendedTimeOut": "1000", 
         "showEasing": "swing", 
         "hideEasing": "linear", 
         "showMethod": "fadeIn", 
         "hideMethod": "fadeOut" 
        } 
        toastr.danger('Offline'); 

       } 
      }); 
     }, 3000); 

这里的处理程序：

<%@ WebHandler Language="VB" Class="handlecb" %> 

    Imports System.Data 
    Imports System.IO 
    Imports System.Data.OleDb 
    Imports System.Web.SessionState 
    Imports System.Web.Security 
    Imports System.Web 

     Public Class handlecb 
      Implements IHttpHandler, System.Web.Session 

State.IRequiresSessionState 

    Dim con As OleDbConnection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Ishaan Patel\Desktop\Paperhome\paperhome_data.accdb") 


Dim cmd As OleDbCommand 
Dim cmd2 As OleDbCommand 
Dim da As OleDbDataAdapter 
Dim ds As New DataSet 
Dim dr As OleDbDataReader 
Dim result As Integer 

Public Sub ProcessRequest(ByVal context As HttpContext) Implements System.Web.IHttpHandler.ProcessRequest 
    Dim threadid As String 
    If Not context.Session("chatsess") Is Nothing Then 
     threadid = context.Session("chatsess") 
     GoTo b 
    Else 
     GoTo a 
    End If 
    b: 
    Dim thread As Integer 
    thread = Convert.ToInt32(threadid) 


    con.Open() 'checklastupdatedon 
    cmd = New OleDbCommand("SELECT [last_updated_on] FROM [message_threads] WHERE ([message_threads].[thread_id] = " & thread & ")", con) 
    cmd.Connection = con 
    dr = cmd.ExecuteReader 
    If (dr.Read) Then 
     Dim fetched As Date = Convert.ToDateTime(dr("last_updated_on")) 
     Dim old As Date = Convert.ToDateTime(context.Session("last_updated_on")) 

     result = DateTime.Compare(old, fetched) 
     con.Close() 

     If result < 0 Then 'old fetched is earlier than timer fetched 

      context.Session("last_updated_on") = fetched 

     End If 

    End If 
    a: 
End Sub 

Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable 
    Get 




    Return result 
    End Get 
End Property 
End Class 

任何帮助/建议表示赞赏。谢谢。

Answer 1

调用处理程序时，函数名缺失。 请更改代码如下：

url: "handlecb.ashx/ProcessRequest", 
type: "POST",