Parse nested JSON with json.net in Visual Basic

Question

I have nested JSON strings that i would like to parse out the appropriate values from much like below. As i am learning by doing I am struggling a little bit, I have the first part working in that I can parse out single JSON strings, and return the appropriate value using code example 1 below, however i am stuck with a JSON string that is problematic in that it is nested, so the same approach won't work

{
  "jsonrpc":"2.0",
  "method":"Player.OnPause",
  "params":{
     "data": { "item": { "id":29, "type":"episode" },
               "player": { "playerid":1, "speed":0 }
             },
     "sender":"xbmc"
  }
}

And the code...

    Dim JSON As String
    Dim values As Newtonsoft.Json.Linq.JObject
    JSON = JSON STRING WOULD GO HERE, COMES from TCP IP STREAM
    values = JObject.Parse(JSON)
    Console.WriteLine(values.GetValue("method"))

Using that example i can extract the method key (e.g. Player.OnPause) from the first level JSON string, but how can i extract data from the second, and third level strings, For example in the above string, being able to get to Data level JSON values, and Item level JSON values. Is this possible in a similar way to the above?

Appreciate any tips you could provide, I am a learn by examples person, but just struggling to apply something to read multiple nested JSON strings, or multiple levels. No doubt it will be an easy thing that i am missing, but id appreciate any help someone could provide.

Thanks

Solution 1

    Dim jsonstring = IO.File.ReadAllText("json.txt")
    Dim jo = Json.Linq.JObject.Parse(jsonstring)
    Dim playerid = jo("params")("data")("player")("playerid")

Do you mean something like this? "json.txt" simply contains your JSON string.

Solution 2

After searching here and else where for an polymorhic example of parsing javascrip object notation into a .net dictionary I gave up and wrote my own. Hope someone finds this useful ;)

Public Class jsonDictionary
    Inherits Dictionary(Of String, Object)

#Region "Public Properties"
    Private _parent As jsonDictionary
    Public ReadOnly Property Parent() As jsonDictionary
        Get
            Return _parent
        End Get
    End Property

#End Region

#Region "Initialisation and Finalisation"

    Public Sub New(ByVal Parent As jsonDictionary, ByVal strJson As String)
        _parent = Parent
        For Each Element As String In SplitJSON(CharTrim(strJson))
            Dim elName As String = CharTrim(Element.Split(":")(0).Trim)
            Select Case Element.Split(":")(1).Trim.Substring(0, 1)
                Case "{"
                    Me.Add(elName, New jsonDictionary(Me, Element.Substring(InStr(Element, ":"))))
                Case "["
                    Dim ElArray As New List(Of jsonDictionary)
                    For Each ArrayElement As String In SplitJSON(CharTrim(Element.Substring(InStr(Element, ":"))))
                        ElArray.Add(New jsonDictionary(Me, ArrayElement))
                    Next
                    Me.Add(elName, ElArray)
                Case Else
                    Me.Add(elName, Element.Split(":")(1).Trim)
            End Select

        Next
    End Sub

#End Region

#Region "Private Methods"

    Public Shared Function CharTrim(ByVal Str As String) As String
        Return Str.Trim.Substring(1, Str.Length - 2)
    End Function

    Private Function SplitJSON(ByVal str As String) As String()

        Dim ret() As String = Nothing
        Dim sqCount As Integer = 0
        Dim clCount As Integer = 0
        Dim buildStr As New System.Text.StringBuilder

        For i As Integer = 0 To str.Length - 1
            Select Case str.Substring(i, 1)
                Case ","
                    If sqCount = 0 And clCount = 0 Then
                        Try
                            ReDim Preserve ret(UBound(ret) + 1)
                        Catch ex As Exception
                            ReDim ret(0)
                        Finally
                            ret(UBound(ret)) = buildStr.ToString
                            buildStr = New System.Text.StringBuilder
                        End Try
                    Else
                        buildStr.Append(str.Substring(i, 1))
                    End If
                Case Else
                    buildStr.Append(str.Substring(i, 1))
                    Select Case str.Substring(i, 1)
                        Case "["
                            sqCount += 1
                        Case "]"
                            sqCount -= 1
                        Case "{"
                            clCount += 1
                        Case "}"
                            clCount -= 1

                    End Select
            End Select
        Next
        If buildStr.ToString.Length > 0 Then
            Try
                ReDim Preserve ret(UBound(ret) + 1)
            Catch ex As Exception
                ReDim ret(0)
            Finally
                ret(UBound(ret)) = buildStr.ToString
            End Try
        End If
        Return ret

    End Function

#End Region

End Class

Comments

[Jeff B]

What happens right now if you do values.GetValue("data") or values.GetValue("player")?