Deserialize complex JSON (VB.NET) - vb.net

Question

I'm trying to deserialize json returned by some directions API similar to Google Maps API. My JSON is as follows (I'm using VB.NET 2008):
jsontext =
{
"version":0.3,
"status":0,
"route_summary":
{
"total_distance":300,
"total_time":14,
"start_point":"43",
"end_point":"42"
},
"route_geometry":[[51.025421,18.647631],[51.026131,18.6471],[51.027802,18.645639]],
"route_instructions": [["Head northwest on 43",88,0,4,"88 m","NW",334.8],["Continue on 42",212,1,10,"0.2 km","NW",331.1,"C",356.3]]
}
So far I came up with the following code:
Dim js As New System.Web.Script.Serialization.JavaScriptSerializer
Dim lstTextAreas As Output_CloudMade() = js.Deserialize(Of Output_CloudMade())(jsontext)
I'm not sure how to define complex class, i.e. Output_CloudMade.
I'm trying something like:
Public Class RouteSummary
Private mTotalDist As Long
Private mTotalTime As Long
Private mStartPoint As String
Private mEndPoint As String
Public Property TotalDist() As Long
Get
Return mTotalDist
End Get
Set(ByVal value As Long)
mTotalDist = value
End Set
End Property
Public Property TotalTime() As Long
Get
Return mTotalTime
End Get
Set(ByVal value As Long)
mTotalTime = value
End Set
End Property
Public Property StartPoint() As String
Get
Return mStartPoint
End Get
Set(ByVal value As String)
mStartPoint = value
End Set
End Property
Public Property EndPoint() As String
Get
Return mEndPoint
End Get
Set(ByVal value As String)
mEndPoint = value
End Set
End Property
End Class
Public Class Output_CloudMade
Private mVersion As Double
Private mStatus As Long
Private mRSummary As RouteSummary
'Private mRGeometry As RouteGeometry
'Private mRInstructions As RouteInstructions
Public Property Version() As Double
Get
Return mVersion
End Get
Set(ByVal value As Double)
mVersion = value
End Set
End Property
Public Property Status() As Long
Get
Return mStatus
End Get
Set(ByVal value As Long)
mStatus = value
End Set
End Property
Public Property Summary() As RouteSummary
Get
Return mRSummary
End Get
Set(ByVal value As RouteSummary)
mRSummary = value
End Set
End Property
'Public Property Geometry() As String
' Get
' End Get
' Set(ByVal value As String)
' End Set
'End Property
'Public Property Instructions() As String
' Get
' End Get
' Set(ByVal value As String)
' End Set
'End Property
End Class
but it does not work. The problem is with complex properties, like route_summary. It is filled with "nothing". Other properties, like "status" or "version" are filled properly.
Any ideas, how to define class for the above JSON?
Can you share some working code for deserializing JSON in VB.NET?
Thanks,

Answer 1

Below is a sample Converter class that will take an incoming stream of JSON and convert to to an object you specify. I should note the below code is .Net 4.0. The JSON serializer in 4 is much easier to use. Let me know if you can't use 4 and I'll see if I can dig up a 3.5 version. Basically you need to create a class structure to map the JSON to a Class. I created the Route and RouteSummary classes for you. I left route_geometry and route_instructions as objects. You should create class definitions for each but this should get you started.
Imports System.IO
Imports System.Runtime.Serialization.Json
Imports System.Runtime.Serialization
<DataContract(Namespace:="")> _
Public Class Route
<DataMember(Name:="version")>
Public Property version As Double
<DataMember(Name:="status")>
Public Property status As Double
<DataMember(Name:="route_summary")>
Public Property route_summary As route_summary
<DataMember(Name:="route_geometry")>
Public Property route_geometry As Object()
<DataMember(Name:="route_instructions")>
Public Property route_instructions() As Object
End Class
<DataContract(Name:="route_summary", Namespace:="")> _
Public Class route_summary
<DataMember(Name:="total_distance")>
Public Property total_distance As Double
<DataMember(Name:="total_time")>
Public Property total_time As Double
<DataMember(Name:="start_point")>
Public Property start_point As Double
<DataMember(Name:="end_point")>
Public Property end_point As Double
End Class
Public Class Converter(Of t)
Public Function ReturnJSON(ByRef sreader As StreamReader) As t
If GetType(t).Equals(GetType(String)) Then
Dim result As Object = sreader.ReadToEnd.Replace("""", "")
Return result
Else
Dim ds As New DataContractJsonSerializer(GetType(t))
Dim result As t = DirectCast(ds.ReadObject(sreader.BaseStream), t)
ds = Nothing
Return result
End If
End Function
End Class
Sub Main()
Dim json As String = "{""version"":0.3, ""status"":0, ""route_summary"": { ""total_distance"":300, ""total_time"":14, ""start_point"":""43"", ""end_point"":""42"" }, ""route_geometry"":[[51.025421,18.647631],[51.026131,18.6471],[51.027802,18.645639]], ""route_instructions"": [[""Head northwest on 43"",88,0,4,""88 m"",""NW"",334.8],[""Continue on 42"",212,1,10,""0.2 km"",""NW"",331.1,""C"",356.3]]}"
Dim encoding As New System.Text.UTF8Encoding
Dim bytes() As Byte = encoding.GetBytes(json)
Using os As New MemoryStream
os.Write(bytes, 0, bytes.Length)
os.Position = 0
Using reader As New StreamReader(os)
Dim converter As New Converter(Of Route)
Dim output As Route
output = converter.ReturnJSON(reader)
'output contains data
End Using
End Using
End Sub
See this page for a detailed description of how to read the JSON data. http://www.json.org/