How do i get access Token in web request vb.net

I have some confusion with web request and newtonsoft.json, I was trying to convert stream reader to newtonsoft.json and get access token value from api. How do i get one value from stream reader to newtonsoft.json.

request example:

{
   "username":"abc",
   "password":"abc123"
}

response example:

{
   "accessToken":"xxxxxxxxxxx",
   "expires": "12355"
}

Code:

            Dim accessToken As String
            Dim jsonObject As String
            Dim body As String = ""
            Dim request As WebRequest = WebRequest.Create("http://xxx.xxx.xxx.xxx/api/getaccessToken")
            body = "{""username"": ""abc"", ""password"": ""abc123""}"
            request.Method = "POST"
            request.ContentType = "application/json"
            request.ContentLength = 0
            Dim bArray As Byte() = Encoding.UTF8.GetBytes(body)
            Dim dStream As Stream = request.GetRequestStream()
            dStream.Write(bArray, 0, bArray.Length)
            dStream.Close()
            Dim streamReader As StreamReader = New StreamReader(request.GetResponse().GetResponseStream)
            Dim streamR = streamReader.ReadToEnd()
            jsonObject = JsonConvert.DeserializeObject(streamR)
            Return jsonObject

How do i get access Token only in my code?

I have found out the solution using newtonsoft.json.linq, I can get the object in the json response.

dim bearerToken = streamR
dim jsonObject as JObject = JObject.Parse(bearerToken)
dim token as string = jsonObject.SelectToken("access_Token").ToString
return token