razzak razzak - 1 year ago 1013
Vb.net Question

How to read JSON http post response using VB

I have the following code, it connects to PHP server and retrieve data successfully, i'm not very good with VB, how can i read the JSON response text and extract it's elements?

Public Class Form1
Private Sub submit_Click(sender As System.Object, e As System.EventArgs) Handles submit.Click
Dim user As String
Dim pass As String
user = uname.Text
pass = passwd.Text

Dim request As WebRequest = WebRequest.Create("http://domain.com/test.php")
request.Method = "POST"
Dim postData As String
postData = "username=" & user & "&password=" & pass
Dim byteArray As Byte() = Encoding.UTF8.GetBytes(postData)
request.ContentType = "application/x-www-form-urlencoded"
request.ContentLength = byteArray.Length
Dim dataStream As Stream = request.GetRequestStream()
dataStream.Write(byteArray, 0, byteArray.Length)
Dim response As WebResponse = request.GetResponse()
Console.WriteLine(CType(response, HttpWebResponse).StatusDescription)
dataStream = response.GetResponseStream()
Dim reader As New StreamReader(dataStream)
Dim responseFromServer As String = reader.ReadToEnd()
If responseFromServer = "0" Then
MsgBox("Login Failed")
MsgBox("json data")
End If
End Sub
End Class

The JSON response would be something like:

{"comments": [
"comment" : "some text",
"date" : "some date",
"user" : "user name"
"comment" : "some text",
"date" : "some date",
"user" : "user name"
"messages": [ .... ]

How to output the json string into:

user date comment
user 1 date 1 comment 1
user 2 date 2 comment 2

user date message
user 1 date 1 message 1
user 2 date 2 message 2

Answer Source

After long research and many tests I found out a very nice extension called Newtonsoft.json, it's extremely simple and can be installed from package manager console like this:

install-package Newtonsoft.json

And include it like this:

Imports Newtonsoft.Json
Imports Newtonsoft.Json.Linq

Then all i needed to do is to declare the elements names and values like this:

    Dim json As String = responseFromServer
    Dim ser As JObject = JObject.Parse(json)
    Dim data As List(Of JToken) = ser.Children().ToList
    Dim output As String = ""

    For Each item As JProperty In data
        Select Case item.Name
            Case "comments"
                output += "Comments:" + vbCrLf
                For Each comment As JObject In item.Values
                    Dim u As String = comment("user")
                    Dim d As String = comment("date")
                    Dim c As String = comment("comment")
                    output += u + vbTab + d + vbTab + c + vbCrLf

            Case "messages"
                output += "Messages:" + vbCrLf
                For Each msg As JObject In item.Values
                    Dim f As String = msg("from")
                    Dim t As String = msg("to")
                    Dim d As String = msg("date")
                    Dim m As String = msg("message")
                    Dim s As String = msg("status")
                    output += f + vbTab + t + vbTab + d + vbTab + m + vbTab + s + vbCrLf

        End Select
End If

hope someone will find this useful

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