I have an ugly JSON string that is getting returned from an API that looks like this (this is the result of Console.Write on the string):
{"d":"\"\\\"\\\\\\\"[{\\\\\\\\\\\\\\\"foo\\\\\\\\\\\\\\\":15,\\\\\\\\\\\\\\\"bar\\\\\\\\\\\\\\\":null}]\\\\\\\"\\\"\\n\""}
I am trying to parse this into a C# object in the simplest way possible, so I can access properties like foo and bar. But I am having a difficult time doing this.
I have tried parsing it a number of ways, including:
// code to get the response string
client.Headers.Add(HttpRequestHeader.ContentType, "application/json");
var serializedData = "{data: 'data'}";
var responseString = client.UploadString(url, "POST", serializedData);
// parse the response string
dynamic obj = Newtonsoft.Json.JsonConvert.DeserializeObject(jsonString);
This allows me to access the value of d, which is the actual string I need to parse. I then tried to parse that separately using JArray.Parse(obj["d"]), but I get an error saying that obj["d"] is not an array.
Unfortunately, I have no access to the API itself so can't modify how it's serializing the data it's returning.
Any suggestions?
You can replace all New Line, Backslash, Double quotes to format the JSON
var formattedJson = jsonString.Replace(#"\n", string.Empty)
.Replace(#"\", string.Empty)
.Replace("\"\"", string.Empty);
Console.WriteLine(formattedJson);
OUTPUT
{
"d": [
{
"foo": 15,
"bar": null
}
]
}
Convert to JArray.
var jArray = JArray.Parse(JObject.Parse(formattedJson)["d"].ToString());
Console.WriteLine($"{jArray[0]["foo"]} {jArray[0]["bar"]}");
OUTPUT
15
The problem is that the value of "d" is a string representing a string representing a string ... representing an array. You could call it JSON serialization "inception".
The way to deal with this is to deserialize the value corresponding number of times. If you're sure that the value is never going to be an actual string, you could do it like this, without having to know how many times the value was serialized:
var myObject = JObject.Parse(s);
var d = myObject["d"];
while(d.Type == JTokenType.String)
d = JToken.Parse(d.ToObject<string>());
myObject["d"] = d;
After this procedure myObject represents this data:
{
"d": [
{
"foo": 15,
"bar": null
}
]
}
Replacing escape characters in fine however I would not rely on the console.write command as the definitive output to examine. Here are a couple of other ways: -
Use Postman to make the API call so you can see the raw result. This will (hopefully) show it in an easy to read format that you can then define your class to deserialise to.
Write the raw response to a “.json” file. Open that file in a good editor (such as VS Code or VS itself) to see how the data is actually structured when it is received.
On a side note I would recommend using RestSharp to do the REST calls and Newtonsoft.Json to do the serialising/deserialising.
Related
Why JArray.Parse(json_array) gives me "{" in front of the result? (it's like an object)
What I missed?
string _s = "[{\"person\": { \"b2b_pid\": \"157\"} }]";
JArray _j = JArray.Parse(_s);
_j returns:
{[
{
"person": {
"b2b_pid": "157"
}
}
]
}
string _s = "[{\"person\": { \"b2b_pid\": \"157\"} }]";
Simply because you are not passing grammatically correct json object.
in some cases,array cannot be the root of a json object,you have to use dictionary to wrap the array even when you only have one array in your json object.
PS: I notice there is new standard that array top lier is supported.However,be careful of code compatibility.
C# statement JArray.Parse(_s); is adequate intelligent to try to fix your json issue While Key missing.
In the code snippet below, the JSON string in the commented out jsonString variable is valid while the uncommented out one causes JObject.Parse to throw a JsonReaderException with the message:
After parsing a value an unexpected character was encountered: e. Path 'Key', line 1, position 15.
var jsonString = "{\"Key\":\"Value \"extra\" \"}";
//var jsonString = "{\"Key\":\"Value \\\"extra\\\" \"}";
JObject.Parse(jsonString);
Are there any methods available in Newtonsoft.Json or elsewhere that can transform a JSON string to make it valid?
No, because NewtonSoft cannot guess what you want. E.g. is extra a new key and did you just ommit a comma or is it part of the previous value, or is it just something that can be ignored. It would be better to have the thing you are consuming the json from construct valid json.
Using Regex might help you to resolve the existing JSON you have. If you can control how subsequent JSON is generated, you really should fix it at that point.
This solution counts the value as existing from the first " after a "key":, through to the last " before a , or a }, and then it reserializes the value to ensure that it is correctly escaped. If it finds ",, it expects it to be followed by another key ("key":). This is in an attempt to avoid red herrings (i.e. {"key": "test "," value"}) which might otherwise confuse it.
private static string FixJson(string json)
{
var regex = new Regex("\"(?<key>.*?)\"\\W?:\\W?\"(?<value>.*?)\"(?=,\".*?\"\\W?:|}$)");
return regex.Replace(json, new MatchEvaluator(m => {
var key = m.Groups["key"].Value;
var val = m.Groups["value"].Value;
return string.Format("\"{0}\":{1}", key, JsonConvert.SerializeObject(val));
}));
}
Disclaimer: It's a regular expression, it's not foolproof, and if your JSON is more broken than you have indicated, it will probably spit out broken JSON, or incorrect values, so use it at your own risk.
Try it online
I'm having troubles de-serializing this JSON string using JSON.NET (note the quotes):
"[]"
Depending on which JSON validation website you go to, this is valid JSON (jsonlint for example says it is).
The JSON.NET code:
void Main()
{
string json = "\"[]\"";
var x = JsonConvert.DeserializeObject<User[]>(json);
Console.WriteLine(x);
}
// Define other methods and classes here
public class User
{
public string Id { get; set; }
public int Age { get; set; }
}
The exception
Error converting value "[]" to type 'UserQuery+User[]'. Path '', line 1, position 4.
Is there a way of forcing JSON.NET to parse this?
Part 1: Is "[]" valid JSON?
There are several documents and standards on JSON, and hundreds of parsers; and some of them suppose that JSON can only be object {} or an array [], but some allow single values like strings, numbers to be used as JSON.
Read this article, it widely describes this problem.
What is the minimum valid JSON?
This dispute on JSON validity is another question. In your case, it doesn't matter, because...
Part 2: why your code isn't working.
Even if we allow non-objects \ non-arrays to be valid JSON, then your JSON represents a single string equal to "[]". It could be anything else, not brackets, it is not an array notation, but just two symbols "[" and "]".
However, you try to parse this JSON as an array of objects, which will anyway result into error.
In other words, even if it is a valid JSON, then it is a valid JSON string, not JSON array.
var str1 = JSON.parse("\"[]\""),
str2 = JSON.parse("\"could be anything else, not brackets\""),
arr = JSON.parse("[]");
console.log(typeof str1);
console.log(typeof str2);
console.log(typeof arr);
var str1_s = JSON.stringify([]);
console.log("Valid JSON of an empty array: " + str1_s);
var arr_s = JSON.stringify("[]");
console.log("Partly valid JSON of a string '[]': " + arr_s);
Part 3: what should you do
The best idea - stop using invalid JSON as input. Tell whoever gave you this JSON that it is invalid JSON array and you cannot use it. You would be able to deserialize a JSON into your array of User if it was correct just like you use it:
string json = "[]";
var x = JsonConvert.DeserializeObject<User[]>(json);
Console.WriteLine(x);
If this JSON is provided from 3rd party services and you can do nothing about that, then you need to tidy it up and make it valid. Yeah, unfortunately, sometimes it happens.
How? It depends on what is your value when there ARE objects (users).
It may be a JSON-serialized JSON-string (double-serialized) like this, and then you need to deserialize a string, and then deserialize an array.
Or it can just have two odd quotes in the beginning and the end, and you can just remove them.
It is valid JSON, but the deserializer failes because the datatypes do not match.
"[]"
Is a string, so the deserializer wants to serialize it to a string.
[]
Is an empty array. So, in short, this should work:
string json = "[]";
var x = JsonConvert.DeserializeObject<User[]>(json);
Console.WriteLine(x);
I get an error while parsing a json string into an object. I am using system.json to parse the json string.
The JSON file: (NOTE: I cannot change the structure of this json file because it is generated)
{
title: "My Title",
log: "",
nid: "1234",
type: "software",
language: "EN",
created: "1364480345",
revision_timestamp: "1366803957",
body: {
und: [
{
value: "abc",
summary: "def"
}
]
}
}
The C# code:
string jsonString = new WebClient().DownloadString(".......MyJson.json"); //For test purpose
var obj = JsonObject.Parse (jsonString); ///<--- At this line the exception is thrown
The Exception:
System.ArgumentException has been thrown.
Invalid JSON string literal format. At line 1, column 2
How to solve this?
Thanks in advance!
You can't. That isn't valid json. Field names must be enclosed in quotes. All json parsing tools will throw when trying to parse that.
You could process it and turn it to valid json before deserializing, but really, you need to correct it API side. No clients will work with that.
How to solve this?
(NOTE: I cannot change the structure of this json file because it is generated)
Easy, use json.Net. it works without any problem with your json
var j = JObject.Parse(jsonString);
You can even use dynamic keyword
dynamic j = JObject.Parse(jsonString);
Console.WriteLine("{0},{1}", j.title, j.body.und[0].value);
I want to directly capture JSON from an external API in a service layer, return that to a MVC 4 ApiController, and then output the JSON through that ApiController. I'm basically writing a wrapper around another API service because some other actions have to happen at the same time (authentication, etc). The problem is that the JSON gets converted to a string and is passed around as a string in my C# code. This just adds escape characters to the JSON. Is there anyway I can just pass the JSON object around in my C# code? Details of my implementation are below.
In a service layer, I'm consuming an API that provides JSON via the method below.
return new WebClient().DownloadString(url);
Unfortunately this returns a string. As this API is already returning JSON to me this is problematic because lots of escape characters get added to the string.
The JSON should look something like this
[{"Citation":{"Attachments":[{"AttachedPersonIds":null,..."Type":"Record"}]
But instead it now looks like this
"[{\"Citation\":{\"Attachments\":[{\"AttachedPersonIds\":null,...\"Type\":\"Record\"}]"
After I get this string I return it through a couple of methods to an ApiController (which is setup to return JSON) like this.
public class HintsController : ApiController
{
public string Get(string treeId, string personId)
{
return _hintService.GetHints(treeId, personId);
}
}
I've tried to convert the string to a Literal string and tried serializing the string again. Doing this just adds more escape characters and doesn't solve the problem. I think the problem is with how I'm consuming the initial call because it's casting it from JSON to a string. But I don't know how to avoid this.
Thanks in advance for any ideas.
Because the controller returns a string, the JSON formatter is serializing the entire string to a JSON string and escaping the embedded quote characters.
You can do something like this:
public HttpResponseMessage Get()
{
var resp = new HttpResponseMessage()
{
Content = new StringContent("{json here...}")
};
resp.Content.Headers.ContentType =
new MediaTypeHeaderValue("application/json");
return resp;
}
This assumes that you always want to return JSON.
You can turn it into a dynamic object and pass that around, if you really want to pass the objects.
I can't tell where the literal escape characters are coming from, can you be a little more clear on that. Is the API generating them, or is there some other point in our code? I've seen them in the debug window before, when the string didn't actually contain them, and printing/etc worked normally.
You can use Json.net (standard), the built in serializer, https://github.com/jsonfx/jsonfx and others .
From the jsonfx site:
var reader = new JsonReader(); var writer = new JsonWriter();
string input = #"{ ""foo"": true, ""array"": [ 42, false, ""Hello!"", null ] }";
dynamic output = reader.Read(input);
Console.WriteLine(output.array[0]); // 42
string json = writer.Write(output);
Console.WriteLine(json); // {"foo":true,"array":[42,false,"Hello!",null]}
There are a few other ways ways, see these threads:
Deserialize json object into dynamic object using Json.net
Deserialize JSON into C# dynamic object?