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Why JArray.Parse(json_array) gives me "{" in front of the result?

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.

Unexpected character encountered while parsing value: ?. Path '', line 0, position 0

I have this JSON file:
[
{
"param1": "someURL",
"param2": "someURL2"
},
{
"param1": "someURL3",
"param2": "someURL4"
}
]
JsonLint says that this JSON is valid.
Now I read this JSON file from Azure Storage download it to a stream and then encode it:
string content = Encoding.UTF8.GetString(memoryStream.ToArray());
Next I want to deserialize this to a list of objects:
List<MyParamObject> deserialized = JsonConvert.DeserializeObject<List<MyParamObject>>(text);
MyParamObject is a POCO with two attributes named Param1 and Param2
When I try to deserialize it I get the following error:
Unexpected character encountered while parsing value: ?. Path '', line 0, position 0.
But I do give JsonConvert a string with a valid JSON what can I do?

Through a HEX Editor I checked the beginning of the file and I found out that my IDE added a BOM to the beginning of the file. So it looks like this:
[.. {.. "
As they are not recommended I chose to get rid of them by creating a new file with Explorer/Finder and adding my JSON in there.

Json returned with space

I'm trying to check if In the json there is a certain property. Actually I can do it in the following way:
var container = (JContainer)JsonConvert.DeserializeObject(responseText);
var x = container.ToString(Formatting.None);
var message = container["text"];
now the variable responseText is returned as:
{[
{
"trace": {
"details": {
"data": "[29-02-2016 17:37:32.931751]",
"type": "[info]",
"text": "[Done.]"
},
"context": {
"context": [
[
{
"ID": "John Dillinger"
}
]
]
}
}
}
]}
in the x variable I have removed the space and the final result is:
"[{\"trace\":{\"details\":{\"data\":\"[29-02-2016 17:37:32.931751]\",\"type\":\"[info]\",\"text\":\"[Done.]\"},\"context\":{\"context\":[[{\"ID\":\"John Dillinger\"}]]}}}]"
Now if the key isn't found I get null:
if (message == null)
{
return responseText;
}
the problem is that I perform the condition on the message variable that check if in the container (not formatted) there is the property, the problem is that I get this exception:
{"Accessed JArray values with invalid key value: \"text\". Int32 array index expected."}
but if I replace container with the second json with the slash all working good. Now my problem is that I can't execute var message= x["text"]; 'cause x is a string. So how I can remove the space in the json and check if contain the text key?

It looks like when you removed the space, you also changed the order of the first brackets In the first example your first brackets are {[, in the second they are [{
In json, the ordering makes a difference. {} means object and [] means array.
[{"data":"value"}] is legal because you are saying that you have an array of an object. {["value"]} is not legal because your object does not have a name for the array. The legal version would be { "data":["value"] }
Here is a handy web tool to verify your JSON syntax

Unable to Parse this Json string in c#

I tried using Newtonsoft.Json to deserialize this json string, but I'm not getting the desired output.
my json string is
[
{
"id": 1,
"key": "Residential Homeowner",
"i18nText": "unknown message code DB_ENUM_UserType_residentialhomeowner",
"i18nKey": "DB_ENUM_UserType_residentialhomeowner"
},
{
"id": 8,
"key": "VAR Dealer \/ Builder",
"i18nText": "unknown message code DB_ENUM_UserType_vardealer\/builder",
"i18nKey": "DB_ENUM_UserType_vardealer\/builder"
},
{
"id": 2,
"key": "Administrator",
"i18nText": "unknown message code DB_ENUM_UserType_administrator",
"i18nKey": "DB_ENUM_UserType_administrator"
},
{
"id": 9998,
"key": "TempGuidUser",
"i18nText": "unknown message code DB_ENUM_UserType_tempguiduser",
"i18nKey": "DB_ENUM_UserType_tempguiduser"
},
{
"id": 9999,
"key": "GuidUser",
"i18nText": "unknown message code DB_ENUM_UserType_guiduser",
"i18nKey": "DB_ENUM_UserType_guiduser"
}
]
I just want the value of key when value of id=1. Generally json starts with {}(curly bracket) but here it is like [](square bracket). I've seen many examples but none worked for me.

Generally json starts with {} (curly bracket), but here it is like [] (square bracket).
This is because you got an array of objects, not a single object. Arrays are serialized with square brackets around them. You should deserialize it into an array, and then grab the object at the index of interest.

This is a related post that addresses JSON parsing in C#: C# JSON Parsing.
If the brackets are a problem, simply use:
string json = inputJson.Trim().Trim('[',']');
If the id can have a minimum value of 1, then this should work:
string GetKey(string inputJson)
{
string key = inputJson.Substring(inputJson.IndexOf("key")+5);
key = key.Substring(key.IndexOf("\""), key.IndexOf(",")-key.IndexOf("\""));
key = key.Trim('\"');
return key;
}

If you are only interested in a single value from that larger JSON value, you may want to try Linq to JSON which would allow you to query over the JSON without deserializing everything.
Example:
JArray values = JArray.Parse(json);
string key;
var keyObject = values.FirstOrDefault(p => (int)p["id"] == 1);
if (keyObject != null)
{
key = (string)keyObject["key"];
}

[] is to define a json object array. Your output should be an array. Traverse through the array like:
for(var i=0; i<output.Length; i++)
{
if(output[i].id == "1") // desired id
{
Console.WriteLine(output[i].key);// use it as you wish
}
}
and use the found objects key.

JSON parse exception using System.Json

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);