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C#, How to unescape characters in JObject values?

I have some Javascript code embedded in some JSON fields.
For example:
{
"elements": [{
"bindingParams": "return field.innerHTML.match(/\\d+/gi).toString();\n"
}]
}
And I want to write this code to a new file. The thing is that when this Javascript is set as a value to a JObject the newlines and other characters as the backslash are being escaped.
I have tried using Regex.Unescape(field.Value<string>()), but I get an error in fields with \\d
The error is parsing 'field.innerHTML.match(/\\d+/gi).toString();' - Unrecognized escape sequence \\d.
I could always go with field.Value<string>().Replace("\\n", "\n).Replace("\\","\").Etc(...) but I don't know the sequences that Newtonsoft JObject is escaping.
I would like to know the escape characters that Newtonsoft uses or a method/function from Newtosoft that allows me to unescape the string.
I appreciate your help. Thanks in advance.

The double backslash "\\d" is causing the problem.
Before parsing the jsonString try to replace them this way:
var jsonString ="{\"elements\": [{\"bindingParams\": \"return field.innerHTML.match(/\\d+/gi).toString();\n\"}]}";
jsonString = jsonString .Replace("\\", "\\\\"); // <=== this line
var o = JObject.Parse(jsonString); // This works !

I found out that the issue was that I was trying to unescape an already unescaped string.
The field.Value<string>() already unescapes the string. So the solution to my issue was just not to call Regex.Unescapeand use the value directly.
Sorry.

safe JSON parsing. How JSON parse can parse UTF characters?

Hello I am wondering why this line doesn't work:
JSON.parse({"a":"\u00A9"})
I tried to serach in MDN website but I didn't find anything referring to in json.parse
Unicode escaping is syntactically legal in js according to this: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#String_literals
What is the problem and how can I safely parse text with JSON.parse

{"a":"\u00A9"} is a JavaScript object literal.
JSON.parse expects to be passed a string so it is implicitly converted to a string ("[object Object]").
The [ is fine, because a JSON text can start with an array.
The o is then an error because it isn't allowed there.
A literal copyright symbol (remember that \u00A9 inside a JavaScript string literal will be consumed by the JS parser before it gets to the JSON parser) or the unicode escape sequence would be fine.
console.log(JSON.parse('{"a":"\u00A9"}'));
console.log(JSON.parse('{"a":"\\u00A9"}'));
Note that creating a string literal in JS source code that contains JSON and then parsing it is a terrible idea. You have to deal with nested levels of escaping, and it is inefficient.
If you have an object: use the object.
var data = {"a":"\u00A9"};
console.log(data.a);

Why can't Javascript parse this JSON array from a string literal?

What I am trying to do is simple. Parse this array holding json objects into a Javascript array.
var merchantsJson = JSON.parse('[{"id":61693,"name":"Más"},{"id":61690,"name":"\u0027\u0022\u003C/div\u003E"}]');
But the unicode character \u003C seems to be breaking the parser. In the chrome console I see "Uncaught SyntaxError: Unexpected token <"
A little more info. The above is what the code is evaluated to. In reality the code contains a jsp expression.
var merchantsJson = JSON.parse('${jsonArr}');
If I remove the single quotes, there is no issue, but eclipse give me an "missing semicolon" error message. Is it possible to parse the array with the quotes as I am trying to do?

The interpolation of ${jsonArr} is already a JavaScript object. When you wrap it in '${jsonArr}' this turns it into a string and you have to use JSON.parse.
There's no need to make it a string. You can just do var merchantsArray = ${jsonArr}. JSON constructs are already interoperable with JavaScript code.

Because there's an extra " in your string literal that is encoded by \u0022:
> '[{"id":61693,"name":"Más"},{"id":61690,"name":"\u0027\u0022\u003C/div\u003E"}]'
[{"id":61693,"name":"Más"},{"id":61690,"name":"'"</div>"}]
In short, your JSON in the string is invalid. You would need to escape the unicode escape sequences for the quotes in the string literal ("'\u0022</div>"), by using
JSON.parse('[{"id":61693,"name":"Más"},{"id":61690,"name":"\u0027\\u0022\u003C/div\u003E"}]'
// ^
or escape the quote character ("'\"</div>"):
JSON.parse('[{"id":61693,"name":"Más"},{"id":61690,"name":"\u0027\\\u0022\u003C/div\u003E"}]');
// ^^
However, there actually is no need to use JSON at all. Just output a JS array literal into your code:
var merchantsJson = ${jsonArr};

Try to replace \u with \\u. If you don't, JSON parser receives already decoded Unicode, which created polluted JSON.

It's not because of \u003C, rather the \u0022 character is causing the issue, since it's a quotation mark and JavaScript treats it literally ending the string.
You need to escape that character: \\u0022 .

you have to use special character in your JSON string, you can escape it using \ character.
you need to replace \ with \\.
[{\"id\":61693,\"name\":\"Más\"},{\"id\":61690,\"name\":\"\\u0027\\u0022\\u003C/div\\u003E\"}]

JSON Lint says it's valid but JSON.parse throws error

I have simple JSON that I need to parse to object. Strangely it doesn't work even though if I copy and paste my JSON string to JSONLint (http://jsonlint.com/) it will show that it's valid.
var string = '{"token":"9eebcdc435686459c0e0faac854997f3","email":"201403050007950","id":"13","updated_at":"2014-03-05 10:34:51","messageguides":"[{\"name\":\"Un-named Messaging Guide 1\",\"pages\":[\"sustainabilitydirectors\",\"marketingnbusinessdevelopmentdirectors\"],\"date\":1394015692958}]"}';
var obj = JSON.parse(string); // Unexpected token n
console.log(obj);

The \ characters in the data are treated as JSON escape characters when you parse the raw JSON.
When you embed that JSON inside a JavaScript string, they are treated as JavaScript escape characters and not JSON escape characters.
You need to escape them as \\ when you express your JSON as a JavaScript string.
That said, you are usually better off just dropping the JSON in to the JavaScript as an object (or array) literal instead of embedding it in a string and then parsing it as a separate step.
var obj = {"token":"9eebcdc435686459c0e0faac854997f3","email":"201403050007950","id":"13","updated_at":"2014-03-05 10:34:51","messageguides":"[{\"name\":\"Un-named Messaging Guide 1\",\"pages\":[\"sustainabilitydirectors\",\"marketingnbusinessdevelopmentdirectors\"],\"date\":1394015692958}]"};

How to deserialize Json object which contain control character using Dojo.fromJson

I am using Dojo.fromJson to convert json string to javascript object, but throw exception. Because, there are control characters such as ',\n,\r in the json string.
How can I solve this problem in dojo? convert json string to javascript object, even if there are control characters.
I use Newtonsoft.JsonConvert.SerializeObject to convert C# oject to json data. Json Object: {"name":"'\"abc\n123\r"} then, I use Dojo.fromJson(' {"name":"'\"abc\n123\r"}') to convert json data to javascript object.
Thank you very much!

Problem, i believe is the double-quote which should be escaped by triple backslashes. You can use "native browser JSON decode" as searchterm for "dojo fromJson" synonym.
Without knowing my way around C# - I havent tested but i believe following should work:
string c_sharp_name = "'\"abc\n123\r";
// C#Object.name
c_sharp_name = c_sharp_name.
replace('"', '\\"'). // maybe add a slash on serverside
replace('\n', '\\\n').
replace('\r', '\\\r');
since
while this fails:
{"name":"'\"abc\n123\r"} // your single backslash
this would work:
{"name":"'\\\"abc\\\n123\\\r"} // working triple backslash escape