ServiceStack.Text reading json results not working - json

Question

I am just trying to figure out the best way to deserialize a json string returned from a 3rd party api call. I read ServiceStack is fast so want to try it out. No experience and here is what I have done:
Opened Visual Studio 2013
Created new project Windows Forms Application
Installed ServiceStack.Text (based on https://servicestack.net/download)
Added a button (btnView) and textbox (txtOutput)
Add code to btnView_Click event
Private Sub btnView_Click(sender As Object, e As EventArgs) Handles btnView.Click
Me.Cursor = Cursors.WaitCursor
Dim wp As New WebPost 'this allows to pass url and return results
wp.URL = "xxxx"
Dim sJSONRetVal As String = wp.Request(String.Empty, True)
'sJSONRetVal return values looks like the following:
'{"complaints":[{"feedback_type":"abuse","subject":"Sales Agent Position"},{"feedback_type":"abuse","subject":"Sales Agent Position"}],"message":"OK","code":0}
'ServiceStack.Text example
Dim t As SMTP_Complaints = ServiceStack.Text.JsonSerializer.DeserializeFromString(Of SMTP_Complaints)(sJSONRetVal)
'For Each xi As SMTP_Complaints In t
' txtOutput.Text &= xi.mail_from & vbCrLf
'Next
wp = Nothing
txtOutput.Text = t.ToString
Me.Cursor = Cursors.Default
End Sub
Public Class SMTP_Complaints
Dim _feedback_type As String = ""
Dim _subject As String = ""
Public Property feedback_type As String
Get
Return _feedback_type
End Get
Set(value As String)
_feedback_type = value
End Set
End Property
Public Property subject As String
Get
Return _subject
End Get
Set(value As String)
_subject = value
End Set
End Property
End Class
The above doesn't seem to get any data. how would I loop through the data returned and return the data from both instances? Just not sure how I need to set this up to read the json data and then be able to output.

Answer 1

Based on the returned JSON of:
{"complaints":[{"feedback_type":"abuse","subject":"Sales Agent Position"},{"feedback_type":"abuse","subject":"Sales Agent Position"}],"message":"OK","code":0}
You will need two DTOs to deserialise this result.
I have used auto implemented properties here to simplify the complexity of the code. If you use an older version of VB, you'll need to expand these out to include a backing field with get and set method.
Public Class SMTP_Complaint
Public Property feedback_type As String
Public Property subject As String
End Class
Public Class SMTP_ComplaintsResponse
Public Property complaints As SMTP_Complaint()
Public Property message As String
Public Property code As Integer
End Class
You need the SMTP_ComplaintsResponse class because your complaints are wrapped in your JSON response.
Then to deserialise the response:
Dim response = JsonSerializer.DeserializeFromString(Of SMTP_ComplaintsResponse)(sJSONRetVal)
And your complaints are then accessible:
For Each complaint As var In response.complaints
Console.WriteLine("Type: {0}, Subject {1}", complaint.feedback_type, complaint.subject)
Next