Develop Reference

extracting a value from a JSON string

I'm working on a Blazor application and I have a Json string from which I'm trying to extract a value.
Json Data looks like this:
{"a1":"a1234","e1":"e1234}
I'm trying to extract the a1 value from this which is "a1234"
My JSON Data is in a string variable, rawJsonData. I'm trying to use the JsonSerializer.Deserialize, but I'm not sure how to completely use it...
#code
{
string rawJsonData = JsonData (this is not the actual data, it's being pulled from elsewhere)
var x = System.Text.Json.JsonSerializer.Deserialize<???>(rawJsonData)
}
is this the right way to approach this? I'm not sure what to put in place of ??? above. Anyone has experience with this.

If you use Newtonsoft, as suggested in another answer, you don't even have to create a class.
JObject temp = JObject.Parse(rawJsonData);
var a1 = temp["a1"];

Create a class:
public class Root
{
public string a1 { get; set; }
public string e1 { get; set; }
}
Then Deserialize it into that class:
var x = System.Text.JsonSerializer.Deserialize<Root>(rawJsonData);
Or use Newtonsoft.Json:
var x = Newtonsoft.Json.JsonConvert.DeserializeObject<Root>(rawJsonData);
To retrieve the value of a1 just call: x.a1

If you want to stick with System.Text.Json and don't want to create a class/struct for the data (why not?), as suggested in comments, you can
var jsonData = "{\"a1\":\"a1234\",\"e1\":\"e1234\"}";
var doc = JsonDocument.Parse(jsonData);
var a1 = doc?.RootElement.GetProperty("a1").GetString();
Of course, a try catch around the conversion would help.

Create json in UWP without JSON.Net

I am trying to create a json formatted string using c# in UWP without JSON.Net, but I am just not understanding how to get there. Let's say I wanted to create the following json dynamically:
[{"id":130},{"id":131},{"id":132},{"id":133},{"id":134}]
From everything I have read, it would seem that I need a class that defines the content of my json. For example:
class accountTypes
{
public int id { get; set; }
public string type { get; set; }
}
From there, it would seem that I only need to create a list of type "accountTypes" and then add each "id" to the list.
List<accountTypes> jsonList = new List<accountTypes>();
int numOfChildren = AccountTypesList.Children.Count;
for (int i = 0; i < numOfChildren; i++)
{
if (((CheckBox)AccountTypesList.Children[i]).IsChecked == true)
{
jsonList.Add(new accountTypes() { id = (int)(double)((CheckBox)AccountTypesList.Children[i]).Tag });
}
}
While I am 99% sure that the above code is very flawed, it does not crash on me, so that is a start at least. What I am struggling with now though is how I would serialize the list "jsonList". Everything I have read thus far either points to JSON.net or the JavaScriptSerializer Class, and not Windows.Data.Json. If I could see a simple example on how to serialize json using Windows.Data.Json, then I could at least visualize what is going on with my list and could correct it accordingly. That being said, how do I serialize an array or a list using Windows.Data.Json?

First of all, there's no built-in JSON-serializer that handles all the mapping for you. This is exactly what JSON.NET is doing for you. Therefore, you have to take the manual and long way.
To create exactly this result:
[{"id":130},{"id":131},{"id":132},{"id":133},{"id":134}]
You have to use the JsonArray class. For example, pass your jsonList object to a method like this:
public string ToJson(List<accountTypes> objectList)
{
var jArray = new JsonArray();
foreach (var at in objectList)
{
jArray.Add(ToJson(at));
}
return jArray.ToString();
}
Whereas you use this method to create a JsonObject for your class object itself (as manual step as well):
public JsonObject ToJson(accountTypes at)
{
var jObj = new JsonObject();
jObj.SetNamedValue("id", JsonValue.CreateNumberValue(at.id));
return jObj;
}

How can I loop through the JSON on Universal Windows Platform with C#

I am developing an app on UWP.
When I connect with a server api and I get the next response I don't have problems.
{"value":"Login successfull","sessionId":"a95077855b05ed0fec5d7fa3abafa126e15aba2a"}
I can get information in the following way:
JsonObject jsonObject = JsonObject.Parse(jsonString);
string token = jsonObject["sessionId"].GetString();
string value = jsonObject["value"].GetString();
but my problem is when i get the next response of the api:
[{"person":{"name":"name1","country":"Spain","city":"user_city","phone":null}},{"person":{"name":"name2","country":"Turkey","city":"user_city","phone":"1111111"}},{"person":{"name":"name3","country":"Argentina","city":"user_city","phone":"22222"}},{"person":{"name":"name4","country":"Argentina","city":"user_city","phone":"33333"}}]
How can I loop through the JSON and get all the people that match a condition?
I have to do with "Windows.Data.Json"

If interested in a solution using only Windows.Data.Json namespace, here it is:
var rootValue = JsonValue.Parse(jsonString);
foreach (var item in rootValue.GetArray())
{
var unamedObject = item.GetObject();
var personObject = unamedObject["person"].GetObject();
System.Diagnostics.Debug.WriteLine(personObject["name"].GetString());
System.Diagnostics.Debug.WriteLine(personObject["country"].GetString());
System.Diagnostics.Debug.WriteLine(personObject["city"].GetString());
System.Diagnostics.Debug.WriteLine(personObject["phone"].GetString());
}
Why would somebody pick Windows.Data.Json over Newtonsoft's Json.net?
If your JSON needs are simple, you can reduce the size of your app ~1 MB by choosing Windows.Data.Json because it is part of the operating system.

I would recommend you try out Json.net nuget package and deserialise the json payload to classes through that.
A good tutorial can be found here: http://windowsapptutorials.com/windows-phone/general/deserialize-json-data-using-newtonsoft-json-net-library/
But if you search you'll find more.
In short, you first copy paste your json and use Visual Studio > File > Paste Special > To paste to classes ( first open an empty cs file and set your cursor inside it ).
After that you use JsonConvert.DeserializeObject<RootObject>() to actually parse the json string.
Once parsed you'll have an array of items if your original json also defined an array.
Note RootObject is the first class object in the generated classes in Visual Studio

There are ways to do it without external libraries, if that is the real reason for the stipulation of Windows.Data.Json.
I'd likely do it something like this...
First I'd make some classes representing the returning JSON:
public class RootObject
{
public Person person { get; set; }
}
public class Person
{
public string name { get; set; }
public string country { get; set; }
public string city { get; set; }
public string phone { get; set; }
}
Then add a little method to deserialize:
public static T Deserialize<T>(string json)
{
var bytes = Encoding.Unicode.GetBytes(json);
using (var ms = new MemoryStream(bytes))
{
var serializer = new System.Runtime.Serialization.Json.DataContractJsonSerializer(typeof(T));
return (T)serializer.ReadObject(ms);
}
}
And finally deserialize and query that result like so:
var persons = Json.Deserialize<List<RootObject>>(textBox.Text);
var peeps = (from p in persons
where p.person.name.StartsWith("name")
select p).ToList();

Can the C# MongoClient be used to return valid JSON without first serializing to a .NET type?

I would like to have ASP.NET MVC return a document stored in MongoDB as JSON, but have no need for it to be serialized to a .NET type first. However, BSONDocument.ToJSON() returns JSON that looks like this:
{_id:ObjectId("someid")}
The browser's JSON parser does not like "ObjectId(nnn)" and so the call fails with a parser error. I am able to get parse-able JSON using a Regex hack:
public ActionResult GetFormDefinitionsJSON()
{
var client = new MongoDB.Driver.MongoClient(ConfigurationManager.ConnectionStrings["mongodb"].ConnectionString);
var db = client.GetServer().GetDatabase("formthing");
var result = db.GetCollection("formdefinitions").FindAll().ToArray();
var sb = new StringBuilder();
sb.Append("[");
var regex = new Regex(#"(ObjectId\()(.*)(\))");
var all = result.Select(x => regex.Replace(x.ToJson(), "$2"));
sb.Append(string.Join(",", all));
sb.Append("]");
return Content(sb.ToString(), "application/json");
}
This returns parse-able JSON:
{_id:"someid"}
But it smells. Is there any way without regex and string building hackery to get the official MongoDB driver to return JSON that can be parsed by the browser? Alternatively, am I missing something on the browser side that would allow {_id:ObjectId("someid")} to be parsed as valid?

You have two options that I can think of.
The first one is to use the JavaScript JsonOutputMode mode. This results in the ID serializing to "_id" : { "$oid" : "51cc69b31ad71706e4c9c14c" } - not quite ideal, but at least it's valid Javascript Json.
result.ToJson(new JsonWriterSettings { OutputMode = JsonOutputMode.JavaScript })
The other option is to serialize your results into an object and use the [BsonRepresentation(BsonType.String)] attribute. This results in much nicer Json: "_id" : "51cc6a361ad7172f60143d97"; however, it requires you to define a class to serialize it in to (this can affect performance)
class Example
{
[BsonId]
[BsonRepresentation(BsonType.String)]
public ObjectId ID { get; set; }
public string EmailAddress { get; set; }
}
// Elsewhere in Code - nb you need to use the GetCollection<T> method so
// that your result gets serialized
var result = database.GetCollection<Example>("users").FindAll().ToArray();
var json = result.ToJson();
Some more details on the differences between JsonOuputModes (Strict, Javascrpt and Mongo):
http://docs.mongodb.org/manual/reference/mongodb-extended-json/

Writing and Reading to a Json format

I have a large object in C# that i would like to write (serialize) to a .json file. I then want to read this .json file and be able to deserialize this object in javascript in order to display it on a website (after formatting it further in javascript). Can anyone tell me how i can achieve this serialization and deserialization to and from a properly formatted json file? Ive tried a few approaches but cant seem to achieve a tree like object structure in outputted file.
Thanks

If you are in a WebService you can set the [ScriptService] tag on your methods. If you are in a winforms or some other kind of app and need to use just serialize an object, you can tag your class serializable and then you can use the JavaSciptSerializer:
[Serializable]
public class MyClas
{
public int intVal { get; set; }
public double doubleVal { get; set; }
public string stringVal { get; set; }
}
In a method:
// Add a reference to System.Web.Extensions
// using System.Web.Script.Serialization;
JavaScriptSerializer jss = new JavaScriptSerializer();
var myClass = new MyClas();
myClass.doubleVal = 42.00;
myClass.intVal = 42;
myClass.stringVal = "The answer";
MessageBox.Show(jss.Serialize(myClass));

JSON Lint could be what you're looking for on the client end. It's a pure javascript json validator/reformatter.
You can test the library here. It takes:
{"example" : "of", "json" : ["being", "reformatted"], "into" : {"something" : "pretty"}}
and makes it:
{
"example": "of",
"json": [
"being",
"reformatted"
],
"into": {
"something": "pretty"
}
}