Need a class/structure to serialize JSON in VB.net

Question

I am trying to figure out a class/struture to handle the following JSON format:

{
"ReturnData": [
    {
        "id": "msg2DoesNotExistName",
        "value": "value 1",
        "userExists": 2 
    },
    {
        "id": "msg2DoesNotExistName",
        "value": "Value 2",
        "userExists": 2 
    } 
],
"SetValue": [
    {
        "id": "msg2DoesNotExistName",
        "value": "value 1" 
    },
    {
        "id": "msg2DoesNotExistName",
        "value": "Value 2" 
    } 
]

}

I have tried (just the SetValue portion):

    <Serializable()> _
Public Class Stuff
            Public SetValue() As ArrayList
End Class

Public Function TestSerial3(ByVal somevar As String) As String
    Dim s As New JavaScriptSerializer()
    Dim ret As String
    Dim b As New SaveType()
   Dim p1 As New Stuff
    b = New SaveType
    b.id = "ctl00_number_1"
    b.value = "Test1"
    p1.SetValue(0).Add(b)

    b = New SaveType
    b.id = "ctl100_number_2"
    b.value = "Test2"
    p1.SetValue(1).Add(b)

    ret = s.Serialize(p1)

    return ret
 end function

This is the result: System.NullReferenceException: Object reference not set to an instance of an object.

I am able to serialize the inside portion using a structure, but cannot figure out how to include the outer name (ReturnData, SetValue) without resorting to string building:

<Serializable()> _
Public Structure UserExistsType
    Public id As String
    Public value As String
    Public userExists As Integer
End Structure

 Dim b(1) As UserExistsType
 b(0).id = "msg2DoesNotExistName"
 b(0).value = "value 1"
 b(0).userExists = 2
 b(1).id = "msg2DoesNotExistName"
 b(1).value = "Value 2"
 b(1).userExists = 2
 ret = s.Serialize(b)
 ret = "{" & Chr(34) & "ReturnData" & Chr(34) & ":" & ret & "}"

I may or may not have Data for ReturnData and SetValue (one or both at a minimum). I am trying to let the serializer handle most of the formatting without having to check for empty sections and single-item arrays. Any suggestions?

score 0 · Answer 1 · answered Mar 10 '11 at 20:33

How bout something like this (I only coded up SetValue, you can easily add ReturnData using the same technique.

Essentially, just wrap your two arrays in an outer object (I called mine MethodCall, because that's what it looks like).

    Imports System.Runtime.Serialization
    Imports System.Web.script.serialization

    Public Class Form1

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
            Debug.Print(TestSerial3())
        End Sub


        Public Function TestSerial3() As String
            Dim s As New JavaScriptSerializer()
            Dim ret As String
            Dim r = New MethodCall
            r.SetValue(0) = New SetValue
            With r.SetValue(0)
                .id = "ctl00_number_1"
                .value = "Test1"
            End With


            r.SetValue(0) = New SetValue
            With r.SetValue(0)
                .id = "ctl100_number_2"
                .value = "Test2"
            End With
            ret = s.Serialize(r)

            Return ret
        End Function

    End Class


    <Serializable()> _
    Public Class ReturnData
        Public id As String
        Public value As String
        Public userExists As Integer
    End Class


    <Serializable()> _
    Public Class SetValue
        Public id As String
        Public value As String
    End Class


    <Serializable()> _
    Public Class MethodCall
        Public SetValue(1) As SetValue
        Public returnData(2) As ReturnData
    End Class

Thanks - this mostly works. Dim R AS New MethodCall and the second id/value pair should use index 1. Outside of the syntax errors, I'm stuck with having to know the number of elements ahead of time. It's a good solution and specifically handles the example I posted. Since my original post, I've moved to using an arraylist and adding each value pair (no need to know the number of elements ahead of time). I'm still using the string concatenation at the end. — user652411, Mar 14 '11 at 13:53

Need a class/structure to serialize JSON in VB.net

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