I think i have have a bug in JSON.Net - debugging

Question

So I'm a bit of a beginner think i've got some unexpected behaviour/ a bug, though it may well be operator error rather than anything else but either way I'm stumped and don't know what to do.
I'm reading in a JSON string! from
https://beta-api.betfair.com/exchange/betting/rest/v1/en/navigation/lhm.json
I'm passing it with JSON.Net(v6.0.3 from Nuget) ill get to how in minute, but im getting a error where two of the supposedly unique objects returned have the same ID, something of a problem. While trying to work out where I had mashed it up I looked at the JSON string with the Visual Studio JSON Visualiser and that is showing two different ID's as expected.
Edit
I've uploaded two pictures but had to od it externally and copied in the section of JSON that's relevant.
http://imgur.com/pk2hIJI,SZDSSLh
{
"children": [
{
"children": [
{
"exchangeId": "1",
"id": "1.114548892",
"name": "Moneyline",
"type": "MARKET"
}
],
"id": "27229997",
"name": "Hamilton # Calgary",
"type": "EVENT"
},
{
"children": [
{
"exchangeId": "1",
"id": "1.114548889",
"name": "Moneyline",
"type": "MARKET"
}
],
"id": "27229996",
"name": "Toronto # Ottawa",
"type": "EVENT"
}
],
"id": "74587734296",
"name": "Games 18 July",
"type": "GROUP"
},
To fetch the string i am using an object inherited from HTTPclient, with
BFresponce = Await Me.GetAsync(BetFairBetaAddress & RestAddress & Method)
Dim x = Await BFresponce.Content.ReadAsStringAsync 'not normaly here just so i can veiw the string
Return JsonConvertHelper.DeserializeObject(Of T)(Await BFresponce.Content.ReadAsStreamAsync())
With my own help function
Public Shared Function DeserializeObject(Of T)(stream As Stream) As T
Dim serializer As New JsonSerializer()
Using streamReader As New StreamReader(stream)
Return serializer.Deserialize(streamReader, GetType(T))
End Using
End Function
And the class beeing passed in T is
Namespace BetFairNS
Public Class NavigationData
Public Property name As String
Public Property id As Single
Public Property exchangeId As Integer
Public Property type As NavigationDataType
Public Property children As List(Of NavigationData)
End Class
Public Enum NavigationDataType
EVENT_TYPE
GROUP
[EVENT]
MARKET
RACE
End Enum
End Namespace
So the crux of it is have i mashed this up somewhere? or if its a bug what do I do?

Answer 1

There is nothing wrong with Json.Net. The JSON data file you linked to has 260 instances of recurring IDs, all of them in the Horse Racing category. Here are the first 5:
Duplicate id found: 1.114591860
Path 1: ROOT > Horse Racing > 1600m 3yo > 1600m 3yo
Path 2: ROOT > Horse Racing > FRA > Chant (FRA) 14th Jul > 1600m 3yo
Duplicate id found: 1.114591859
Path 1: ROOT > Horse Racing > 1600m 3yo > To Be Placed
Path 2: ROOT > Horse Racing > FRA > Chant (FRA) 14th Jul > To Be Placed
Duplicate id found: 1.114591864
Path 1: ROOT > Horse Racing > 1600m 3yo > 1600m 3yo
Path 2: ROOT > Horse Racing > FRA > Chant (FRA) 14th Jul > 1600m 3yo
Duplicate id found: 1.114591863
Path 1: ROOT > Horse Racing > 1600m 3yo > To Be Placed
Path 2: ROOT > Horse Racing > FRA > Chant (FRA) 14th Jul > To Be Placed
Duplicate id found: 1.114591869
Path 1: ROOT > Horse Racing > 1600m Grp1 > 1600m Grp1
Path 2: ROOT > Horse Racing > FRA > Chant (FRA) 14th Jul > 1600m Grp1
You can check this simply by downloading the file using a web browser, saving it to disk, then opening it with a text editor and searching for the ID values I've listed. Each one appears twice, at different places in the hierarchy.
Does it say somewhere in the API documentation for this site that all IDs in the JSON will be distinct? It looks to me like they simply decided to list the same node at more than one level for browsing convenience (i.e. list all the races directly under "horse racing" and also list them by country/event). You are probably going to need to change your assumptions about the data and adjust your code accordingly.
EDIT
Now that you have shared the actual ID / name of the node that is giving you trouble, the problem is clear. You've declared the id field of your NavigationData class as Single when it should be String. Single is a floating point type, and is not suitable for holding ID values, even if they may have a decimal point in them.
Again, take a closer look at the actual JSON file. If you search for "Hamilton # Calgary", you will see that it has an ID of 27229997. The other node, "Toronto # Ottawa", immediately beneath it, has an ID of 27229996. In your debugger image, the values both show as 27229996.0 The IDs are getting mangled most likely because Single does not have the capability to represent the number 27229997 exactly as a binary floating point number, so the closest neighboring value is being chosen instead. This is a very bad thing when you need an exact representation (as you always do with an ID).
The key point is to use the right tool for the job. You cannot assume that a third-party ID will always be numeric or contain only a single decimal point, and you will never do math operations on an ID. In short, there's no reason to make it a decimal type. Declare it as String and that will fix the problem. I would also recommend the same for the exchangeId field for the same reason.