Question

请按以下方式对Web API进行AJAX调用

$.ajax({
         type: "POST",
         url: "CustomerService.asmx/GetAccounts",
         data: '{"custid":"' + cusID + '"}',
         contentType: "application/json; charset-utf-8",
         dataType: "json",
         success: function (data) {
             datatableVariable = $('#dtAccounts').DataTable({.......

这是我的ASP.NET Web方法

<WebMethod()>
Public Sub GetAccounts(ByVal custid As Integer)


    Dim sql As String = "Select * from Accounts WHERE CustomerID =" & custid & " Order by ID"

    Dim constr As String = ConfigurationManager.ConnectionStrings("flashCon").ConnectionString
    Dim accs = New List(Of Accounts)()
    Using con As New SqlConnection(constr)
        Using cmd As New SqlCommand(sql)
            cmd.CommandType = CommandType.Text
            cmd.Connection = con
            con.Open()
            Dim dr = cmd.ExecuteReader()
            If dr.HasRows Then
                While dr.Read
                    Dim acc = New Accounts() With {
                   .custID = Convert.ToInt32(dr("CustomerID").ToString()),
                    .AccNum = dr("AccountNumber").ToString(),
                    .Descri = dr("Description").ToString(),
                    .CurrBalance = dr("CurrentBalance").ToString(),
                    .typOA = dr("TypeOfAccount").ToString(),
                    .Frozen = dr("Frozen").ToString()
                    }
                    accs.Add(acc)
                End While
            End If
        End Using
    End Using
    Dim js = New JavaScriptSerializer()
    Dim strResponse As String = js.Serialize(accs)
    Context.Response.Write(strResponse)
End Sub

返回的JSON字符串响应是下面的另外一个奇怪的{＆＃34; d＆＃34;：null}值，我不知道它来自哪里

[{"custID":2,"AccNum":"KODSW00002","Descri":"","CurrBalance":0,"Frozen":false,"typOA":0}]{"d":null}

如果我使用Context.Response.Flush()它会消失，但我会从浏览器Server cannot clear headers after HTTP headers have been sent.

收到另一个错误

有人可以协助我解决这个问题，现在已经好几个星期了吗

非常感谢

Answer 1

不推荐使用JavascriptSerializer。它早在大多数事实上的JSON标准之前创建，当然在任何实际标准之前。例如，它不使用事实上的ISO8601日期格式。

微软的own documentation在最顶层说：

Json.NET应该用于序列化和反序列化。为支持AJAX的应用程序提供序列化和反序列化功能。

Microsoft本身在ASP.NET MVC Web API中使用Json.NET。

使用Json.NET ，您可以使用JsonConvert.Serialize从对象列表生成Json字符串：

Dim strResponse As String = JsonConvert.Serialize(accs)

Answer 2

尝试一下

$.ajax({
     type: "POST",
     url: "CustomerService.asmx/GetAccounts",
     data: {custid: cusID},
     dataType: "json",
     success: function (data) {
         alert(data.d); // Should correctly get the response in the d variable.

秘密在于JavaScriptSerializer不需要 contentType：“应用程序/ json； charset-utf-8”，

，并且数据中的参数没有撇号或直接用双引号引起来

更多信息，请访问：https://www.youtube.com/watch?v=Zq_aMDFeCCA

致谢

Answer 3

在使用Context.Response.Clear()在服务器端提供响应并设置contentType之前，我们必须从ASP.NET Web服务中清除默认响应 {d：null} 。

Context.Response.Clear()
Context.Response.ContentType = "application/json"
Context.Response.AddHeader("content-length", stringJSON.Length.ToString())
Context.Response.Flush()
Context.Response.Write(stringJSON)
HttpContext.Current.ApplicationInstance.CompleteRequest()

Answer 4

你得到{＆＃34; d＆＃34;：null}，因为你的WebMethod没有返回值，你只是写入Response对象。

您应该从方法中返回一个字符串：

Public Sub GetAccounts(ByVal custid As Integer) As String

Dim sql As String = "Select * from Accounts WHERE CustomerID =" & custid & " Order by ID"

Dim constr As String = ConfigurationManager.ConnectionStrings("flashCon").ConnectionString
Dim accs = New List(Of Accounts)()
Using con As New SqlConnection(constr)
    Using cmd As New SqlCommand(sql)
        cmd.CommandType = CommandType.Text
        cmd.Connection = con
        con.Open()
        Dim dr = cmd.ExecuteReader()
        If dr.HasRows Then
            While dr.Read
                Dim acc = New Accounts() With {
               .custID = Convert.ToInt32(dr("CustomerID").ToString()),
                .AccNum = dr("AccountNumber").ToString(),
                .Descri = dr("Description").ToString(),
                .CurrBalance = dr("CurrentBalance").ToString(),
                .typOA = dr("TypeOfAccount").ToString(),
                .Frozen = dr("Frozen").ToString()
                }
                accs.Add(acc)
            End While
        End If
    End Using
End Using
Dim js = New JavaScriptSerializer()
Dim strResponse As String = js.Serialize(accs)

<strike>Context.Response.Write(strResponse)</strike>

替换为：

Return strResponse

End Sub

然后返回的对象将是{＆＃34; d＆＃34;：＆＃34; [{＆＃34; custID＆＃34;：2，＆＃34; AccNum＆＃34;：＆＃34; KODSW00002＆＃34;＆＃34; Descri＆＃34;：＆＃34;＆＃34;＆＃34; CurrBalance＆＃34;：0，＆＃34;冷冻及＃34;：假，＆＃34; typOA＆＃34;：0}]＆＃34;}，可以通过javascript中的response.d进行访问。

$.ajax({
         type: "POST",
         url: "CustomerService.asmx/GetAccounts",
         data: '{"custid":"' + cusID + '"}',
         contentType: "application/json; charset-utf-8",
         dataType: "json",
         success: function (data) {
             alert(data.d); // Should correctly get the response in the d variable.

https://stackoverflow.com/a/20471116/4008833

在JSON响应中有奇怪的{＆＃34; d＆＃34;：null}

4 个答案: