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How to parse a complicated nested JSON string in C#?

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.

Convert string into a valid JSON in c#

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

Is "[]" valid JSON?

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);

Json get array object from JSON Object C#

I have this json string passed to my webapi
string jsonstring = "{\"datamodel\": \"[{\"K1\":\"V1\",\"K2\":\"V2\"}]\"}";
I may have more than on pair of (K,V) inside. How do i parse this in C# ?
I thought i could first convert my string to a JObject and get the key for datamodel from that and then use JArray to parse the K,V. But its throwing a jsonreader exception on the first line of code here
JObject my_obj = JsonConvert.DeserializeObject<JObject>(jsonstring.ToString());
and then do this..
JObject data = my_obj["datamodel"].Value<JObject>();

First of all, the JSON string you are posting is not valid. Given your comment, you can clean up the quotes before and after the square brackets using this snippet:
string jsonstring = "{\"datamodel\": \"[{\"K1\":\"V1\",\"K2\":\"V2\"}]\"}";;
string jsonstringCleaned = jsonstring.Replace("\"[", "[").Replace("]\"", "]");
var my_obj = JsonConvert.DeserializeObject<JObject>(jsonstringCleaned);

The code is right, but the exception you are getting is related to the formatting of your JSON string. If you put valid JSON in this code, it should work as expected.

There are \" missing around V1 in your JSON string.
It should look like this:
string jsonstring = "{\"datamodel\": \"[{\"K1\":\"V1\",\"K2\":\"V2\"}]\"}";

First always make sure that you have a valid Json string. A simple way to do that is paste it into a Json to C# converter tool, such as this one: http://json2csharp.com/
It may be simpler and more readable to use single quotes within your Json string if that is an option, as it avoids the need to escape the double quotes:
string jsonstring = "{'datamodel': [{'K1':'V1','K2':'V2'}]}"
Now we deserialize the object and get the JArray. There is no need to call the ToString() on the JSON jsonstring string.
var my_obj = JsonConvert.DeserializeObject<JObject>(jsonstring);
var data = (JArray)my_obj["datamodel"];
A better and more concise way to accomplish the same result could be to just use JObject.Parse. We can accomplish the same result with just one line of code.
var data = (JArray)JObject.Parse(jsonstring)["datamodel"];

Json: how to properly strip the escape characters with json.net

I have json response in the below format.
"[{\\\"JobID\\\":\\\"1\\\",\\\"BillGenerationDate\\\":\\\"4/29/2013 2:53:34 PM\\\",\\\"BillID\\\":\\\"115743\\\",\\\"BillNo\\\":\\\"115743\\\",\\\"CustomerID\\\":\\\"4041705\\\",\\\"PayStatus\\\":\\\"0\\\",\\\"PaymentRequiredStatus\\\":\\\"True\\\",\\\"ProductName\\\":\\\"Epic FBO test\\\",\\\"Description\\\":\\\"Epic Automation 2\\\\r\\\\n\\\",\\\"ProductType\\\":\\\"eBill \\\",\\\"DueType\\\":\\\"-1\\\",\\\"DueDate\\\":\\\"2013-03-15\\\",\\\"Amount\\\":\\\"63.70\\\",\\\"Cost\\\":\\\"\\\"},
{\\\"JobID\\\":\\\"9\\\",\\\"BillGenerationDate\\\":\\\"5/2/2013 10:21:39 AM\\\",\\\"BillID\\\":\\\"115743\\\",\\\"BillNo\\\":\\\"115743\\\",\\\"CustomerID\\\":\\\"4041705\\\",\\\"PayStatus\\\":\\\"0\\\",\\\"PaymentRequiredStatus\\\":\\\"True\\\",\\\"ProductName\\\":\\\"FBO Test Product\\\",\\\"Description\\\":\\\"FBO Product Test\\\",\\\"ProductType\\\":\\\"eBill \\\",\\\"DueType\\\":\\\"-1\\\",\\\"DueDate\\\":\\\"2013-05-01\\\",\\\"Amount\\\":\\\"150.70\\\",\\\"Cost\\\":\\\"\\\"}]
I believe json.net handles the escape characters and I used the below code to deserialize it to a dictionary collection.
var billList = JsonConvert.DeserializeObject<List<Dictionary<string, string>>>(contentCorrected);
But this json parsing throws exception
"Invalid property identifier character: . Path '[0]', line 1, position 2."
Could we solve this by manipulating the json response string?

THE SHORT ANSWER: first you need to deserialize the escaped string, but not to the target CLR type, but deserialize to another string (repeat if necessary); then, it is deserialized to the target type:
// Initial example json string: "\"{\\\"Property1\\\":1988,\\\"Property2\\\":\\\"Some data :D\\\"}\""
// First, deserialize to another string (unescaped string).
string unescapedJsonString = JsonConvert.DeserializeObject<string>(escapedJsonString);
Debug.WriteLine(unescapedJsonString);
// Prints:
// "{\"Property1\":1988,\"Property2\":\"Some data :D\"}"
// Second, deserialize to another string, again (in this case is necessary)
var finalUnescapedJsonString = JsonConvert.DeserializeObject<string>(unescapedJsonString);
Debug.WriteLine(finalUnescapedJsonString);
// This time prints a final, unescaped, json string:
// {"Property1":1988,"Property2":"Some data :D"}
// Finally, perform final deserialization to the target type, using the last unescaped string.
MyClass targetObject = JsonConvert.DeserializeObject<MyClass>(finalUnescapedJsonString);
LONG ANSWER (but interesting)
Using string.Replace(... could generate an invalid string, because it could damage certain special characters that needed the backslash to be deserialized correctly .
This type of escaped strings are usually generated when a string that was already a json string, its serialized again (or even more times). This causes something like "various levels of serialization" (it really is a serialization of a string with reserved characters), and the result is backshash characters (or groups of one, two or more backslash followed: \, \, \\\) scattered all over the string.
So, to remove them correctly is not enough to replace them by empty.
THE RIGHT WAY: A better way to get a unescaped string would be to do a first deserialization to string type (Repeat this several times if necessary), And then do a final deserialization to target CLR type:
// -- SERIALIZATION --
// Initial object
MyClass originObj = new MyClass { Property1 = 1988, Property2 = "Some data :D" };
// "First level" Of serialization.
string jsonString = JsonConvert.SerializeObject(originObj);
Debug.WriteLine(jsonString);
// Prints:
// {"Property1":1988,"Property2":"Some data :D"}
// "Second level" of serialization.
string escapedJsonString = JsonConvert.SerializeObject(jsonString);
Debug.WriteLine(escapedJsonString);
// "{\"Property1\":1988,\"Property2\":\"Some data :D\"}"
// Note the initial and final " character and de backslash characters
// ...
// at this point you could do more serializations ("More levels"), Obtaining as a result more and more backslash followed,
// something like this:
// "\"{\\\"Property1\\\":1988,\\\"Property2\\\":\\\"Some data :D\\\"}\""
// Note that is... very very crazy :D
// ...
// -- DESERIALIZATION --
// First deserialize to another string (unescaped string).
string unescapedJsonString = JsonConvert.DeserializeObject<string>(escapedJsonString);
Debug.WriteLine(unescapedJsonString);
// Prints:
// {"Property1":1988,"Property2":"Some data :D"}
// ...
// at this point you could repeat more deserializations to string, if necessary. For example if you have many backslash \\\
// ...
// Finally, perform final deserialization to the target type, using the last unescaped string.
MyClass targetObject = JsonConvert.DeserializeObject<MyClass>(unescapedJsonString);

Try string contentCorrected = contentCorrected.Replace(#"\", "");before deserialization process.

Remove all the "\" character before you deserialize it. Use replace function.
yourJsonString.Replace("\\\\\", "");
Your Json string is incomplete or doesnot seems to be of type List<Dictionary<string, string>>". Correct the type you want the json to be converted.
I modified your json a little as follows and it worked.
newJson = "{ \"array\":" + yourJsonString + "}"

The problem occurs when valid double quotes are used within the answer. Removing and/or Replacing won't solved this in all cases.
It frustrated me too until I found a simple solution:
var billList = JsonConvert.DeserializeObject<List<Dictionary<string, string>>>(#contentCorrected);

For me the code below works
string contentCorrected = contentCorrected.Replace(**#"\""", ""**);