Question

我正在开发一个VB.NET webform项目，我正在尝试使用ajax调用一个函数，然后返回一个以html显示的对象。

这是我的ajax电话：

  $(document).ready(function () {
    msgClickedClass.click(function (event) {
        msgID = event.target.id;
        //Get message body
        $.ajax({
            type: "POST",
            url: "/secure/PortalMessages.aspx/PrintMessageContent",
            data: JSON.stringify({ "msgID": msgID }),
            contentType: 'application/json; charset=utf-8',
            dataType: 'json',
            success: function (data) {
                // $("#dialogText").html(data.d.message);

                alert("success");
            },
            error: function (xhr, status, error) {
                alert('Error: ' + status + '\nError Text: ' + error);
            }
        }) //end ajax


    }); //end click function
  });

这是我的vb函数由ajax调用：

<WebMethod()> _
Public Shared Function PrintMessageContent(msgID As Integer) As Messages
    Dim msg As New Messages

    Dim db As New DB_SQL()

    msg = db.GetSpecificMessageSent(msgID)
    Return msg
End Function

当我调试代码时，我确实有一个应该返回的Messages对象，但是ajax函数失败并返回500错误，而不是“请求在此上下文中不可用”。

当我更改PrintMessageContent以返回字符串而不是对象时，ajax函数成功。

任何建议都将不胜感激。

更新：以下是我的Messages类的内容

    Public Class Messages
Private _TimeStamp As DateTime
Private _Subject As String
Private _Message As String
Private _Agent As String
Private _Id As Integer
Private _MessageViewHistory As List(Of MessagesViewed)

Public Property TimeStamp() As DateTime
    Get
        Return _TimeStamp
    End Get
    Set(value As DateTime)
        _TimeStamp = value
    End Set
End Property

Public Property Subject() As String
    Get
        Return _Subject
    End Get
    Set(value As String)
        _Subject = value
    End Set
End Property

Public Property Message() As String
    Get
        Return _Message
    End Get
    Set(value As String)
        _Message = value
    End Set
End Property

Public Property Agent() As String
    Get
        Return _Agent
    End Get
    Set(value As String)
        _Agent = value
    End Set
End Property

Public Property Id() As Integer
    Get
        Return _Id
    End Get
    Set(value As Integer)
        _Id = value
    End Set
End Property



Public Property MessageViews() As List(Of MessagesViewed)
    Get
        Return _MessageViewHistory
    End Get
    Set(value As List(Of MessagesViewed))
        _MessageViewHistory = value

    End Set
End Property

Public Property MessageHTMLFormat() As String
    Get
        Dim retn As String
        retn = Me.Message.Replace(vbCrLf, "<br />")
        Return retn

    End Get
    Set(value As String)

    End Set
End Property



End Class

更新＃2：新功能：

 <WebMethod()> _
<ScriptMethod(ResponseFormat:=ResponseFormat.Json)> _
Public Shared Function PrintMessageContent(msgID As Integer) As String
    Dim msg As New Messages

    Dim db As New DB_SQL()

    msg = db.GetSpecificMessageSent(msgID)

    Dim serializer As New JavaScriptSerializer()
    Dim serializedResult = serializer.Serialize(msg)
    Return serializedResult
End Function

Answer 1

所有你定义的返回数据类型为JSON，因此你需要指定返回类型：

<WebMethod()> _
<ScriptMethod(ResponseFormat:=ResponseFormat.Json)> _

在文件的顶部，您需要指定脚本服务

Inherits System.Web.Services.WebService

最后你必须将对象转换为JSON

 Dim serializer As New JavaScriptSerializer()
 Dim serializedResult = serializer.Serialize(db.GetSpecificMessageSent(msgID))
 Return serializedResult

<强>更新我注意到你从ajax JSON.stringify({ "msgID": msgID })发送对象但从不使用反序列化。这样做的目的是什么？无论如何你只需发送ID就可以改变你的代码：

url: "/secure/PortalMessages.aspx/PrintMessageContent",
data: { "msgID": msgID },
dataType: 'json',

这也应该有所帮助。

实际上如果你还是喜欢使用stringify格式中的一个小错误。我在webservice中遇到了同样的错误。试试这个：

data: "{'msgID':'" + JSON.stringify(msgID) + "'}",

此格式可帮助您避免类似以下错误：无法解析JSON原语。

Answer 2

我发现问题出在我的Messages类中。出于某种原因，当我查看Messages对象时，它返回的不仅仅是指定的属性。它提供了诸如Buffer, Content-Type, etc之类的东西。

我将Messages类更改为this，当我将鼠标悬停在Messages对象上时，它只会提供指定的属性。

希望这可以节省一些时间和挣扎。

Public Class Messages

Public TimeStamp As DateTime
Public Subject As String
Public Message As String
Public Agent As String
Public Id As Integer
Public MessageViews As List(Of MessagesViewed)

End Class

Ajax函数返回“请求在此上下文中不可用”

2 个答案: