Matching JSON keys to class fields inexactly

Question

I am trying to deserialize a JSON stream into a VB.NET object. However, whenever I try to assign the values to fields in an object, one of the fields doesn't compile because the JSON field includes a hyphen, and to my understanding I need to match my field names and the JSON key names exactly. This is an example of the JSON:

{
    "email":"[email protected]",
    "sg_event_id":"VzcPxPv7SdWvUugt-xKymw",
    "sg_message_id":"142d9f3f351.7618.254f56.filter-147.22649.52A663508.0",
    "timestamp":1386636112,
    "smtp-id":"<[email protected]>",
    "event":"processed",
    "category":["category1","category2","category3"],
    "id":"001","purchase":"PO1452297845","uid":"123456"
}

This JSON example comes from a test stream (via POST) to a webhook designed to communicate with SendGrid's Event Webhook API (https://sendgrid.com/docs/API_Reference/Webhooks/event.html)

I have a class that the JSON is assigned to, shown here:

Partial Class SendGridEvent
    Public email As String
    Public sg_event_id As String
    Public sg_message_id As String
    Public timestamp As String
    Public smtp-id As String
    Public [event] As String
    Public category() As String
    Public id As String
    Public purchase As String
    Public uid As String
    Public reason As String
    Public ip As String
    Public useragent As String
    Public url As String
    Public status As String
    Public type As String
End Class

I have successfully gotten all of the fields except one (smtp-id) to assign correctly whenever a stream comes through. This is accomplished thus (ignore the list declaration, SendGrid sends email information in batches, but I worry it will clutter the example even more):

' Create new stream reader to take in serialized JSON from SendGrid
Dim oSR = New StreamReader(Request.InputStream)
' Store entire stream in new String variable called sContent
Dim sContent As String = oSR.ReadToEnd()

' Declare a new list of SendGridEvent objects
Dim masterOutput = New List(Of SendGridEvent)
' Declare new SendGridEvent objects within the list called masterOutput
Dim a = New SendGridEvent
Dim b = New SendGridEvent
Dim c = New SendGridEvent
Dim d = New SendGridEvent

' Assign individual SendGridEvent object just created to the list of SendGridEvents
masterOutput.Add(a)
masterOutput.Add(b)
masterOutput.Add(c)
masterOutput.Add(d)
' Assign the deserialized JSON String to the BulkEmail array named output, via BulkEmail array deserialization
Dim res = JsonConvert.DeserializeObject(Of List(Of SendGridEvent))(sContent)

' Declare String to use in For Each loop
Dim sContentPair As String = ""

' Write the info from each SendGridEvent in the master SendGridEvent list (masterOutput) to the variable sContentPair
For Each data As SendGridEvent In res
    sContentPair = sContentPair + " => " + data.email + " => " + data.sg_event_id + " => " + data.sg_message_id + _
        " => " + data.timestamp + " => " + data.smtp-id + " => " + data.event + " => " + data.category(0) + " => " + data.id _
    + " => " + data.purchase + " => " + data.uid + " => " + data.reason + " => " + data.ip + " => " + data.useragent _
    + " => " + data.url + " => " + data.status + " => " + data.status + " => " + data.type + " STOP "
Next

Using the JSON example stream from above, this is what outputs (I apologize for the untidy format):

=> [email protected] => VzcPxPv7SdWvUugt-xKymw => 
142d9f3f351.7618.254f56.filter-147.22649.52A663508.0 => 1386636112 => 
=> processed => category1 => 001 => PO1452297845 => 123456 => => => 
=> => => => STOP

The property smtp-id in the SendGridEvent class won't compile because the hyphen ends the indentifier declaration. So, the smtp-id field from the JSON stream cannot assign itself to a property in the object. I have tried using the field name smtp_002D_id instead to force a hyphen in the field name (hence how I managed to get the example output, otherwise the program doesn't compile) but as you see no value is then assigned.

I have looked through over 50 web pages and through several books to find a solution to this general problem. I am not familiar with serialization/deserialization other than what you see here, and I have yet to find a good reference as to exactly how values are assigned to class properties (whether the property names need to match the JSON key names exactly, if they need to be in the exact order the stream spits out, etc.).

ANSWER BELOW

Thanks to Tim and Juan, the solution was fairly quick. Attaching a JsonProperty attribute to the field allowed the JSON stream to correctly be assigned to the correct properties. Corrected code below:

Partial Class SendGridEvent
    <JsonProperty("email")>
    Public Email As String
    <JsonProperty("sg_event_id")>
    Public SgEventId As String
    <JsonProperty("sg_message_id")>
    Public SgMessageId As String
    <JsonProperty("timestamp")>
    Public Timestamp As String
    <JsonProperty("smtp-id")>
    Public SmtpId As String
    <JsonProperty("event")>
    Public EmailEvent As String
    <JsonProperty("category")>
    Public Category() As String
    <JsonProperty("id")>
    Public Id As String
    <JsonProperty("purchase")>
    Public Purchase As String
    <JsonProperty("uid")>
    Public UId As String
    <JsonProperty("reason")>
    Public Reason As String
    <JsonProperty("ip")>
    Public Ip As String
    <JsonProperty("useragent")>
    Public UserAgent As String
    <JsonProperty("url")>
    Public Url As String
    <JsonProperty("status")>
    Public Status As String
    <JsonProperty("type")>
    Public Type As String
End Class

Answer 1

You should use the JsonProperty attribute to let Json.NET know that smtp-id maps to your field.

Partial Class SendGridEvent
    Public email As String
    Public sg_event_id As String
    Public sg_message_id As String
    Public timestamp As String
    <JsonProperty("smtp-id")>
    Public smtp_id As String
    Public [event] As String
    ...

You might want to use this for other fields as well, if it helps your code be clearer. E.g. you should probably pick a non-keyword name for your event field, and you might want to follow the .NET standards of PascalCase instead of the JSON-style under_scores (e.g. SgEventId instead of sg_event_id).

Also, those should (almost certainly) all be properties, not fields.

Answer 2

I come up with this problem once, I just made replace in this case smtp-id for smtpid and then make the serialization.

Change the class property to smtpid and everything must work.

Following the answer of Tim I came up with this class and made a test and works. You need to add using Newtonsoft.Json;

     public class DataClass
            {
                public string email { get; set; }
                public string sg_event_id { get; set; }
                public string sg_message_id { get; set; }
                public int timestamp { get; set; }

                 [JsonProperty("smtp-id")]
                public string smtp { get; set; }
                 [JsonProperty("event")]
                   public string eve { get; set; }
                public List<string> category { get; set; }
                public string id { get; set; }
                public string purchase { get; set; }
                public string uid { get; set; }
            }



This code is from a console app test:


               string json = "{";
    json += "\"email\":\"[email protected]\"" + ",";
    json +="\"sg_event_id\":\"VzcPxPv7SdWvUugt-xKymw\"" + "," ;
    json += "\"sg_message_id\":\"142d9f3f351.7618.254f56.filter-147.22649.52A663508.0\"" + ",";
   json += "\"timestamp\":1386636112" + ",";
   json += "\"smtp-id\":\"<[email protected]>\"" + ",";
   json += "\"event\":\"processed\"" + ",";
   json += "\"category\":[\"category1\",\"category2\",\"category3\"]" + ",";
   json += "\"id\":\"001\",\"purchase\":\"PO1452297845\",\"uid\":\"123456\"" ;
   json +="}";

            DataClass data = JsonConvert.DeserializeObject<DataClass>(json);

            Console.Read();