How to make sure that string is valid JSON using JSON NET

Question

I have a raw string  I just want to validate whether the string is valid JSON or not  I m using JSON NET

User · Accepted Answer

Through Code  Your best bet is to use parse inside a try-catch and catch exception in case of failed parsing   I am not aware of any TryParse method    Using JSON Net  Simplest way would be to Parse the string using JToken Parse  and also to check if the string starts with   or   and ends with   or   respectively  added from this answer   private static bool IsValidJson string strInput        if  string IsNullOrWhiteSpace strInput     return false       strInput   strInput Trim        if   strInput StartsWith  quot   quot    amp  amp  strInput EndsWith  quot   quot         For object          strInput StartsWith  quot   quot    amp  amp  strInput EndsWith  quot   quot       For array               try                       var obj   JToken Parse strInput               return true                    catch  JsonReaderException jex                          Exception in parsing json             Console WriteLine jex Message               return false                    catch  Exception ex    some other exception                       Console WriteLine ex ToString                 return false                      else               return false           The reason to add checks for   or   etc was based on the fact that JToken Parse would parse the values such as  quot 1234 quot  or  quot  a string  quot  as a valid token  The other option could be to use both JObject Parse and JArray Parse in parsing and see if anyone of them succeeds  but I believe checking for    and    should be easier   Thanks  RhinoDevel  for pointing it out  Without JSON Net You can utilize  Net framework 4 5 System Json namespace  like  string jsonString    quot someString quot   try       var tmpObj   JsonValue Parse jsonString     catch  FormatException fex          Invalid json format     Console WriteLine fex     catch  Exception ex    some other exception       Console WriteLine ex ToString         But  you have to install System Json through Nuget package manager using command  PM gt  Install-Package System Json -Version 4 0 20126 16343 on Package Manager Console   taken from here  Non-Code way  Usually  when there is a small json string and you are trying to find a mistake in the json string  then I personally prefer to use available on-line tools  What I usually do is   Paste JSON string in JSONLint The JSON Validator and see if its a valid JSON  Later copy the correct JSON to http   json2csharp com  and generate a template class for it and then de-serialize it using JSON Net

User · Answer

JToken Type is available after a successful parse  This can be used to eliminate some of the preamble in the answers above and provide insight for finer control of the result  Entirely invalid input  e g     ----   IsValidJson    will still throw an exception        public static bool IsValidJson this string src                try                       var asToken   JToken Parse src               return asToken Type    JTokenType Object    asToken Type    JTokenType Array                    catch  Exception      Typically a JsonReaderException exception if you want to specify                        return false                    Json Net reference for JToken Type  https   www newtonsoft com json help html T Newtonsoft Json Linq JTokenType htm

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Just to add something to  Habib s answer  you can also check if given JSON is from a valid type  public static bool IsValidJson lt T gt  this string strInput        if string IsNullOrWhiteSpace strInput   return false       strInput   strInput Trim        if   strInput StartsWith  quot   quot    amp  amp  strInput EndsWith  quot   quot         For object          strInput StartsWith  quot   quot    amp  amp  strInput EndsWith  quot   quot       For array               try                       var obj   JsonConvert DeserializeObject lt T gt  strInput               return true                    catch    not valid                                    return false                      else               return false

User · Answer

I found that JToken Parse incorrectly parses invalid JSON such as the following      Id        Status    2     Paste the JSON string into http   jsonlint com  - it is invalid   So I use   public static bool IsValidJson this string input        input   input Trim        if   input StartsWith       amp  amp  input EndsWith            For object          input StartsWith       amp  amp  input EndsWith          For array               try                         parse the input into a JObject             var jObject   JObject Parse input                foreach var jo in jObject                                string name   jo Key                  JToken value   jo Value                     if the element has a missing value  it will be Undefined - this is invalid                 if  value Type    JTokenType Undefined                                        return false                                                    catch  JsonReaderException jex                          Exception in parsing json             Console WriteLine jex Message               return false                    catch  Exception ex    some other exception                       Console WriteLine ex ToString                 return false                      else               return false             return true

User · Answer

Regarding Tom Beech s answer  I came up with the following instead   public bool ValidateJSON string s        try               JToken Parse s           return true            catch  JsonReaderException ex                Trace WriteLine ex           return false            With a usage of the following   if  ValidateJSON strMsg         var newGroup   DeserializeGroup strMsg

User · Answer

Here is a TryParse extension method based on Habib s answer   public static bool TryParse this string strInput  out JToken output        if  String IsNullOrWhiteSpace strInput                 output   null          return false            strInput   strInput Trim        if   strInput StartsWith       amp  amp  strInput EndsWith            For object          strInput StartsWith       amp  amp  strInput EndsWith          For array               try                       output   JToken Parse strInput               return true                    catch  JsonReaderException jex                          Exception in parsing json               optional  LogError jex               output   null              return false                    catch  Exception ex    some other exception                         optional  LogError ex               output   null              return false                      else               output   null          return false            Usage   JToken jToken  if  strJson TryParse out jToken            work with jToken   else          not valid json

User · Answer

This method doesn t require external libraries  using System Web Script Serialization  bool IsValidJson string json                try               var serializer   new JavaScriptSerializer                dynamic result   serializer DeserializeObject json               return true            catch   return false

User · Answer

Building on Habib s answer  you could write an extension method   public static bool ValidateJSON this string s        try               JToken Parse s           return true            catch  JsonReaderException ex                Trace WriteLine ex           return false            Which can then be used like this   if stringObject ValidateJSON             Valid JSON

User · Answer

Use JContainer Parse str  method to check if the str is a valid Json  If this throws exception then it is not a valid Json   JObject Parse - Can be used to check if the string is a valid Json object JArray Parse - Can be used to check if the string is a valid Json Array JContainer Parse - Can be used to check for both Json object  amp  Array

User · Answer

Alternate option using System Text Json For  Net Core one can also use the System Text Json namespace and parse using the JsonDocument  Example is an extension method based on the namespace operations  public static bool IsJsonValid this string txt        try   return JsonDocument Parse txt     null    catch         return false

User · Answer

I m using this one     internal static bool IsValidJson string data           data   data Trim         try                if  data StartsWith       amp  amp  data EndsWith                            JToken Parse data                     else if  data StartsWith       amp  amp  data EndsWith                            JArray Parse data                     else                      return false                    return true              catch                return false

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