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C#: Appending Json Object to a Json file already containing data

I have created an object which contains data I want to insert/append to the data currently sitting in a json file.
I have succeeded in getting to to write the data to the file however it overwrites all the data that was there originally.
What i am trying to do is append this Property to the json file whilst keeping all the original information.
This is what I have done so far:
string widthBox = Width.Text.ToString();
string heightBox = Height.Text.ToString();
string WindowSizejson = File.ReadAllText(DownloadConfigFilelocation);
dynamic WindowSizejsonObj = Newtonsoft.Json.JsonConvert.DeserializeObject(WindowSizejson);
JObject windowContent = new JObject(
new JProperty("externalSite",
new JObject(
new JProperty("webLogin",
new JObject(
new JProperty("window", "height=" + heightBox + ",width=" + widthBox + ",resizable,scrollbars")
)
)
)
)
);
This is the data currently in the json file that i need to append the above to.
( have blurred out values due to company security reasons)

You have two choices that I can think of:
1.Read the entire file into an object, add your object, and then
rewrite the entire file (poor performance)
var filePath = #"path.json";
// Read existing json data
var jsonData = System.IO.File.ReadAllText(filePath);
// De-serialize to object or create new list
var SomeObjectList= JsonConvert.DeserializeObject<List<T>>(jsonData)
?? new List<T>();
// Add any new
SomeObjectList.Add(new T()
{
Name = "..."
});
SomeObjectList.Add(new T()
{
Name = "..."
});
// edit
var first = SomeObjectList.FirstOrDefault();
first.Name = "...";
// Update json data string
jsonData = JsonConvert.SerializeObject(SomeObjectList);
System.IO.File.WriteAllText(filePath, jsonData);
Open the file read/write,
parse through until you get to the closing curly brace, then write
the remaining data, then write the close curly brace (not trivial)

Instead of messing around with JProperty, deserialize your json and append your desired data:
JObject obj = JObject.Parse(jsontext);
obj["new_prop"] = "value";//new property as per hirarchy ,same for replacing values
string newjson=obj.ToString();
it's much cleaner and easier to maintain.

Cannot Parse JSON in UWP

I created an application on UWP whose data is parsed to JSON with JSON as below:
JSON
I'm having trouble parsing json on "jawaban" and an error message appears like below:
Code:
JsonArray jsonDataOption = groupObjectSoal["jawaban"].GetArray();
foreach (JsonValue groupValueOption in jsonDataSoal)
{
JsonObject groupObjectOption = groupValueSoal.GetObject();
string oid = groupObjectOption["oid"].GetString();
string option = groupObjectOption["q_option"].GetString();
string score = groupObjectOption["score"].GetString();
QuizOption pilihan = new QuizOption();
pilihan.OID = oid;
pilihan.Option = option;
pilihan.Score = score;
}
How to handle it?
Note:
For the full code, can be seen here

Property "list_soal" contains an array with two elements. The first element does not have property "jawaban", so your code fails on parsing first element

Use JSON.net
Newtonsoft
There are plenty examples on the site.
It will automatically fill your data model.
You can deserialize to object by calling.
YourObject m = JsonConvert.DeserializeObject<YourObject>(json);
where json is your json string and YourObject is your model

Check if user is on list

I have Array in JSON file. File looks like this:
["Maverick", "rick", "Rick", "prick", "rick_07"]
I have a username. I want to check if this username is in Array.
public string UserToCheck = "rick";
So im reading json file from URL...
using (var webClient = new System.Net.WebClient())
{
var json = webClient.DownloadString("http://example.ex/users.json");
// Here I want to check if user is on list
}
}
But how Can I check if "UserToCheck" exactly match one of users from array?

You could parse your Json with the great Newtonsoft Json Library:
var users = JsonConvert.DeserializeObject<List<string>>(json);
users.Contains(UserToCheck);
As this is case sensitive, you could use LINQ: users.Any(u => String.Equals(u, UserToCheck, StringComparison.OrdinalIgnoreCase))

Trying parsing the object using JSON parsing. This requires placing the JSON string object into JSON.Parse method.
This portion may be missing:
JObject jObj = JObject.Parse(json);
Console.WriteLine(jObj);
Helpful links: http://www.newtonsoft.com/json/help/html/ParseJsonObject.htm
http://masnun.com/2011/07/08/quick-json-parsing-with-c-sharp.html
To check the string for names, break the names up into a list with C# and iterate through that to check the results.

Newtonsoft Object serialized to String. JObject instance expected

Hi so am trying to parse this JSON line but i got some others that are like this in files thats why i want to automate this so i can remove the invalid lines to make the file a valid JSON for reading, The problem is that the JSON contains multiple JSON in 1 line
Example:
{"item":"value"}{"anotheritem":"value"}
Is there anyway to remove
{"anotheritem":"value"}
So it turns in to a valid JSON that is readable to start parsing the files
I tried doing using StreamReader cause there in a file i have multiple files that contain these invalid JSON
So i got it to be able to detect the Invalid JSON but for some reason i can't get it to read the JSON so i can use .remove to remove the invalid line
using (StreamReader r = new StreamReader(itemDir))
{
string json = r.ReadToEnd();
if (json.Contains("anotheritem"))
{
JObject NoGood = JObject.FromObject(json);
MessageBox.Show(NoGood.ToString());
}
}
The Error:
Object serialized to String. JObject instance expected.
Thank you all for your time and help.

If each object are side by side without space or any other character, you can convert your string to an json array.
string value = "{\"item\":\"value\"}{\"anotheritem\":\"value\"}";
string arrayValue = "[" + value.Replace("}{", "},{") + "]";
var array = JArray.Parse(arrayValue);
var goopArray = array.OfType<JObject>().Where(o => o.Property("anotheritem") == null);
Edit : see my second answer. More robust solution. More modern. And support dotnet core builtin json serializer.

Json.Net
Even better solution, Json.NET have a builtin feature for this exact scenario. See Read Multiple Fragments With JsonReader
The JsonTextReader have a property SupportMultipleContent that allow to read consecutive items when set to true
string value = "{\"item\":\"value\"}{\"anotheritem\":\"value\"}";
var reader = new JsonTextReader(new System.IO.StringReader(value));
reader.SupportMultipleContent = true;
var list = new List<JObject>();
while (reader.Read())
{
var item = JObject.Load(reader);
list.Add(item);
}
System.Text.Json
If you want to use System.Text.Json, it's also acheivable. They are no SupportMultipleContent property but Utf8JsonReader will do the job for you.
string value = "{\"item\":\"value\"}{\"anotheritem\":\"value\"}";
var bytes = Encoding.UTF8.GetBytes(value).AsSpan();
var list = new List<JsonDocument>();
while (bytes.Length != 0)
{
var reader = new Utf8JsonReader(bytes);
var item = JsonDocument.ParseValue(ref reader);
list.Add(item);
bytes = bytes.Slice((int) reader.BytesConsumed);
}

Remove new lines in JSON string using Newtonsoft JSON.NET

I am using Newtonsoft JSON.NET to create a dynamic JSON object which looks fine, but is unrecognizable when I send it to a REST API. My best guess is there are new lines in the JSON string which is breaking the process the API uses to parse the data. Is there a way to ensure all new lines are removed from the JSON data I am sending?
dynamic MyPerson = new JObject();
MyPerson.username = "CodeMonkey";
MyPerson.first_name = "Monkey";
MyPerson.last_name = "banana";
MyPerson.email_address = "bananacrazy#monkey.com";
MyPerson.is_active = true;
string PersonData = JsonConvert.SerializeObject(MyPerson);
The JSON it is returning if I use Response.Write is:
{"username":"CodeMonkey","first_name":"Monkey","last_name":"Banana","email_address":"monkey#bananacrazy.com","is_active":true}