Develop Reference

Read value from nested Json object

I am trying to read a value from a nested Json object, but I am getting a Parse error:
My Json object:
{
"MessageId": "f6774927-37cf-4608-b985-14a7d86a38f9",
"Time": "2017-04-06T16:28:38.0719933+02:00",
"Data":
{
"ID":
{
"value": "0008044834"
},
"Carrier":
{
"value": 0
},
"Tool":
{
"value": 0
}
}
}
var myJsonString = File.ReadAllText(_currentDictory.FullName + #"\test\" + completeFilename);
var myJObject = JObject.Parse(myJsonString);
var serial = myJObject.SelectToken("Data.ID").Value<String>();
System.InvalidCastException
HResult=0x80004002
Message=Cannot cast Newtonsoft.Json.Linq.JObject to Newtonsoft.Json.Linq.JToken.
Source=Newtonsoft.Json
Reading other values such as "MessageID" works withou any problems, but as soon as I try to get "Data.XYZ" I am getting the error above.

You need to add value to your json path:
var serial = myJObject.SelectToken("Data.ID.value").Value<String>();
Your current path selects JObject containing one property named value and you can't convert it directly to string.

MessageId is a string. So you can directly read its value.
Data on the other hand contains objects (see the { and } ). Therefor you need to use
var serial = myJObject.SelectToken("Data.ID.value").Value<String>();
Also see:
Getting 'Cannot cast Newtonsoft.Json.Linq.JObject to Newtonsoft.Json.Linq.JToken' when retrieving items from JSON

C# JSON Deserialise / Get Data Pair from Data Name at Runtime

I want to create a method with the C# Newtonsoft library that can take in a parameter value to return the JSON data value, without needing to know and create a class beforehand, but all I can find are examples to deserialise into a class or into a dynamic object, both needing to know JSON structure prior at development time
Here's an example of what the kind of JSON format I'm expecting, but is subject to change:
{
"Input":
[
{
"Name": "foo"
},
{
"Name": "bar"
},
]
"Output":
[
{
"Name": "bob"
},
{
"Name": "builder"
},
]
}
I'm locked into using Newtonsoft library to work on the JSON file, or do it myself from scratch as it's an embedded system.

You can use JObject. If you deserialize a class without the type it will be deserialized to JObject. You would access your JObject values with named index which is obviously your property name. Other type of interest to you is JArray. This all resides in namespaces:
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
Example:
So the example with your JSON would be:
var json = #"{
""Input"":
[
{ ""Name"": ""foo"" },
{ ""Name"": ""bar"" }
],
""Output"":
[
{ ""Name"": ""bob"" },
{""Name"": ""builder""}
]
}";
var obj = JsonConvert.DeserializeObject(json) as JObject;
var input = obj["Input"] as JArray;
var inputArray = input[0]["Name"];
This would get the first element in array that is in Input field - "foo".

C# - parse JSON with dynamic and access property name with colon

When getting a JSON with property with :
i.e.
{
"root": {
"sim:names": [{
"name": "Tom"
},
{
"name": "David"
}]
}
}
I'm using Newtonsoft Dynamic parse.
var data = JsonConvert.DeserializeObject<dynamic>(jsonString);
I'm trying to access
data.root.sim:names
But getting compilation error "Invalid expression term ':'"
How can I access it?

You should convert it to object
var data = JsonConvert.DeserializeObject<Object>(jsonString);
And access it like this:
var value = ((JObject)data)["root"]["sim:names"];

JSON.net - Write into JSON / JObject using path string

I have a little utility where we extract values from JSON using JObject.SelectToken(path). We need to determine the paths at run-time. Works perfectly.
What I now need to do is to write back into the JSON (JObject or other) using the same path string. I've hunted and searched and I can't quite find if there is anything that does this quite as cleanly as SelectToken does for reading.
(I'm also stuck in 3.5 CF)
For example, something like:
... JObject read in already ...
var theJToken = theJObject.SelectToken("animals.cat[3].name");
theTJoken.SetValue("Bob"); // Of course this doesn't exist
... serialize it ...

JToken.SelectToken actually returns a JToken which can be modified using JToken.Replace. You can use that to replace the node within your JSON object, mutating the original object.
JObject o = JObject.Parse(#"{ 'cats': [
{ 'name': 'cat 1' },
{ 'name': 'cat 2' },
{ 'name': 'cat 3' } ] }");
// get the token
JToken secondCatName = o.SelectToken("cats[1].name");
// replace the name
secondCatName.Replace("meow");
// and the original object has changed
Console.WriteLine(o.ToString());
// { "cats": [ { "name": "cat 1" }, { "name": "meow" }, { "name": "cat 3" } ] }

JSON element reader .NET

I have a simple JSON example like this :
{
"items": {
"element": ["item 1","item 2"]
},
"name": "James"
}
and a JSON Schema like this :
{
'type': 'object',
'properties': {
'name': {'type':'string'},
'items': {
'type': 'object',
'properties':{
'element':{
'type':'array',
'items':[{'type':'string', 'type':'string'}]
}
}
}
},
'additionalProperties': false
}
Calling "IsValid()" method in JSON.NET using the given Schema and Data will return VALID.
Question :
How do I traverse and edit the elements inside JSON ?
My objective is to look-up values of node "element" in database and then replace it with a generalized value if they exists e.g "item 1" exists in database and will replaced with "general value A". However, "item 2" doesn't exist in database and should throw some kind of error message when IsValid() method is called.
Note that this is a desktop application using .NET 4.5 and JSON.NET library, and it will be used as a data-cleansing tool. I'm open to any kind of alternative libraries as long as they are compatible with .NET 4.5 though..

Not fully understand the part of your question with IsValid() issue, but if talk about traversing through json elements and editing, you can use 2 methods.
Install Newtonsoft.Json at first in Package-Manager in VS: Install-package newtonsoft.json.
Create class JsonItems, which describes your input JSON hierarchy
class JsonItems
{
public Items items;
public string name;
}
class Items
{
public List<string> elements { get; set; }
}
Now you can legally deserialize your json and edit result as any .net object.
string jsonItems = #"{
'items': {
'element': ['item 1','item 2']
},
'name': 'James'
}";
var result = JsonConvert.DeserializeObject<JsonItems>(jsonItems);
result.items = new Items
{
elements = new List<string> {"itemd 3", "item 4"}
};
2. The second way is more quick (in implementation), but less secuarble in runtime. With help of dynamic.
dynamic d = JObject.Parse(jsonItems);
d.items.element[1] = "item 3";