如何为 JQUERY 数据表返回 JSON 数据？

Question

如何生成 JSON 数据用于绑定 JQUERY 数据表？

我在 ASP.net Web 服务 (.asmx) 中使用以下代码

<WebMethod()> _
Public Function Getcdata() As String
    Dim dt As New DataTable()
    Using con As New SqlConnection(IDvar.Constr)
        Using cmd As New SqlCommand("Select * from COMPLAINTTYPE", con)

            con.Open()
            Dim da As New SqlDataAdapter(cmd)
            da.Fill(dt)
            Dim serializer As New System.Web.Script.Serialization.JavaScriptSerializer()
            Dim rows As New List(Of Dictionary(Of String, Object))()
            Dim row As Dictionary(Of String, Object)
            For Each dr As DataRow In dt.Rows
                row = New Dictionary(Of String, Object)()
                rows.Add(row)
            Next
            Context.Response.Write(serializer.Serialize(dt))

            con.Close()
            cmd.Dispose()
            dt.Clear()
        End Using
    End Using
End Function

但这会返回错误。请检查我哪里错了

我在调用 web 方法时遇到的错误如下：

System.InvalidOperationException: A circular reference was detected while serializing an object of type 'System.Reflection.RuntimeModule'.
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeCustomObject(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat)

Answer 1

问题出现在这一行：

Context.Response.Write(serializer.Serialize(dt))

您正在尝试将DataTable 实例直接序列化为JavaScriptSerializer 实例，该实例接受IEnumerable 或Dictionary(Of TKey, TValue) 等集合对象。通常你需要的是使用AsEnumerable()和[Select]() LINQ方法转换成IEnumerable：

Dim list = dt.AsEnumerable().[Select](Function(row) New With { Key
    .id = row("COMPLAINTID"), Key
    .name = row("COMPLAINTNAME"), 

    ' other DataTable columns here
}).ToList()

Context.Response.Write(serializer.Serialize(list))

但是由于您有一个包含要序列化的对象的Dictionary(Of String, Object) 列表，因此只需将字典传递给序列化程序，而不是传递DataTable：

Dim rows As New List(Of Dictionary(Of String, Object))()
Dim row As Dictionary(Of String, Object)
For Each dr As DataRow In dt.Rows
    row = New Dictionary(Of String, Object)()
    rows.Add(row)
Next

' pass the list of dictionary here
Context.Response.Write(serializer.Serialize(rows))

旁注：

您可以尝试 JSON.NET 中的JsonConvert.SerializeObject() 方法来序列化包含Dictionary(Of TKey, TValue) 对象的列表，它比JavaScriptSerializer.Serialize() 方法具有更好的字典处理能力。请注意，您应该检查输出以确保 JSON 字符串的格式正确。