How to deserialize Json with fix named elements dynamically in vb.net? - json

Question

I’m on the way to implement an interface to the Ameritrade Rest API in a vb.net application (with httpclient).
Amongst other things, I have to query quotes from a ticker list (e.g. AMD,MSFT,AMZN, ....).
The call of the API works without problems, I get a valid Json back, but the Json is not given back in a way, I would expect.
I now search the best way to handle that problem...
This is not the first interface to a Rest API, I have implemented.
Normally, I implement a corresponding data class in vb.net and then use JsonConvert (from Newtonsoft) to deserialize the Json string into my data class.
Example:
Dim oObject As New DataClass
oObject = JsonConvert.DeserializeObject(Of DataClass)(JsonString)
whereby DataClass is the vb.net class that is defined according to the data in the Json string.
Problem:
The ticker symbol-list to query is dynamic and can change from api call to api call.
If I - e.g. - query AMD and MSFT in a call, I get back (cut to only a few fields) the following Json:
{
"AMD": {
"assetType": "EQUITY",
"symbol": "AMD",
"description": "Advanced Micro Devices, Inc. - Common Stock",
"bidPrice": 92.11
},
"MSFT": {
"assetType": "EQUITY",
"symbol": "MSFT",
"description": "Microsoft Corporation - Common Stock",
"bidPrice": 243.1
}
}
To be able to deserialize the Json, I would have to implement the following DataClass:
Public Class DataClass
Public Property AMD As AMD
Public Property MSFT As MSFT
End Class
Public Class AMD
Public Property assetType As String
Public Property symbol As String
Public Property description As String
Public Property bidPrice As Double
End Class
Public Class MSFT
Public Property assetType As String
Public Property symbol As String
Public Property description As String
Public Property bidPrice As Double
End Class
This would work but is absolutely static and does not make any sense, as I would have to implement a (identical) class for any ticker, I maybe want to query in the feature.
I would expect to get back a dynamic list so that I could implement the class as following:
Public Class DataClass
Public Property TickerDetails As List(Of TickerDetail)
End Class
Public Class TickerDetail
Public Property assetType As String
Public Property symbol As String
Public Property description As String
Public Property bidPrice As Double
End Class
This way, I would be able to deserialize in a List of TickerDetails and the go thru the list (no matter, which symbols I queried).
But, I can’t change, what I get back over the API...
Question:
What is the best way to handle this problem?

Answer 1

You should create a class to represent the a generic stock and then use DeserializeObject to deserialize it into a Dictionary(Of String, [classname]) where the Key represents the stock symbol and the value represents the class.
Take a look at this example:
Public Class Stock
Public Property assetType As String
Public Property symbol As String
Public Property description As String
Public Property bidPrice As Double
End Class
'...
Dim stocks = JsonConvert.DeserializeObject(Of Dictionary(Of String, Stock))(response)
Example: Live Demo

Answer 2

First thanks for the comments.
I ended up to do it completely different now...
I had further problems with the Ameritrade API:
Some fields are named with leading numbers (52WkHigh and 52WkLow) and
vb.net dev's know, that VB.net don't like properties in classes that
are named with a leading number
So I had to "patch" the received Json data and change the names on the fly to other names ("52WkHigh" to "dble52WkHigh" and "52WkLow" to "dble52WkLow") to be able to deserialize
over the data class, what is not nice
Further, I finally need the data (as fast as possible) in a data table and had "a long way to go":
get data -> deserialize to the data class -> walk thru the data class and overtake the data in the data table.
So.. my new solution (with JObject):
Note: needs:
Imports Newtonsoft.Json.Linq
Code snippets:
Create data table in memory:
Dim dtErgebnis As New DataTable
Dim drTemp As DataRow
With dtErgebnis.Columns
.Add("symbol", System.Type.GetType("System.String"))
.Add("lastPrice", System.Type.GetType("System.Double"))
.Add("lastSize", System.Type.GetType("System.Int32"))
.Add("quoteTime", System.Type.GetType("System.DateTime")) ' Note: is a Long in Json
...
End With
Parse the Json-String and fill the datatable:
get the data over httpclient (in JsonString)...
Dim oJson As JObject = JObject.Parse(JsonString) ' creates children tokens
Dim results As List(Of JToken) = oJson.Children().ToList
For Each item As JProperty In results
item.CreateReader()
drTemp = dtErgebnis.NewRow() ' create a new row to data table in memory
' Fill the fields
drTemp("symbol") = item.Value("symbol")
drTemp("lastPrice") = item.Value("lastPrice")
drTemp("lastSize") = item.Value("lastSize")
drTemp("quoteTime") = GetUTCDateFromTimeStamp(item.Value("quoteTimeInLong")).AddHours(1) ' original Long
...
' Add the new row to the data table
dtErgebnis.Rows.Add(drTemp)
' Save the changes
dtErgebnis.AcceptChanges()
Next
Additional note: The Ameritrade API gives back the time stamps as long (additional hurdle), but I (and I think also you;-) want it as datetime.
Therefore the Long (I think this data type comes from Java/Unix) has to be "translated" to datetime = vb.net function GetUTCDateFromTimeStamp below:
Public Function GetUTCDateFromTimeStamp(TimeStamp As Long) As DateTime
Static startTime As New DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)
Return startTime.AddMilliseconds(TimeStamp)
End Function
Additional note:
As I want to have the Swiss time, I add one hour to the UTC time.
So.. this a real good solution for me (exactly for the Ameritrade API).
And.. it's blazing fast... (I get 19 tickers with all fields and show the result (data table) in a data grid).
All together took < 1 Second ("felt" about 500 ms)
Hope this helps somebody...