How to escape JSON string

Question

Are there any classes functions available to be used for easy JSON escaping  I d rather not have to write my own

User · Answer

There s a Json library at Codeplex

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I ran speed tests on some of these answers for a long string and a short string   Clive Paterson s code won by a good bit  presumably because the others are taking into account serialization options  Here are my results   Apple Banana System Web HttpUtility JavaScriptStringEncode  140ms System Web Helpers Json Encode  326ms Newtonsoft Json JsonConvert ToString  230ms Clive Paterson  108ms    some long path with lots of things to escape some long path t with lots of n things to escape some long path with lots of  things to escape some long path with lots  of things to escape System Web HttpUtility JavaScriptStringEncode  2849ms System Web Helpers Json Encode  3300ms Newtonsoft Json JsonConvert ToString  2827ms Clive Paterson  1173ms   And here is the test code   public static void Main string   args        var testStr1    Apple Banana       var testStr2       some long path with lots of things to escape some long path t with lots of n things to escape some long path with lots of   things to escape some long path with lots   of things to escape        foreach  var testStr in new     testStr1  testStr2                  var results   new Dictionary lt string List lt long gt  gt              for  var n   0  n  lt  10  n                          var count   1000   1000               var sw   Stopwatch StartNew                for  var i   0  i  lt  count  i                                  var s   System Web HttpUtility JavaScriptStringEncode testStr                             var t   sw ElapsedMilliseconds              results GetOrCreate  System Web HttpUtility JavaScriptStringEncode   Add t                sw   Stopwatch StartNew                for  var i   0  i  lt  count  i                                  var s   System Web Helpers Json Encode testStr                             t   sw ElapsedMilliseconds              results GetOrCreate  System Web Helpers Json Encode   Add t                sw   Stopwatch StartNew                for  var i   0  i  lt  count  i                                  var s   Newtonsoft Json JsonConvert ToString testStr                             t   sw ElapsedMilliseconds              results GetOrCreate  Newtonsoft Json JsonConvert ToString   Add t                sw   Stopwatch StartNew                for  var i   0  i  lt  count  i                                  var s   cleanForJSON testStr                             t   sw ElapsedMilliseconds              results GetOrCreate  Clive Paterson   Add t                      Console WriteLine testStr           foreach  var result in results                        Console WriteLine result Key          Math Round result Value Skip 1  Average       ms                      Console WriteLine               Console ReadLine

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The methods offered here are faulty   Why venture that far when you could just use System Web HttpUtility JavaScriptEncode   If you re on a lower framework  you can just copy paste it from mono Courtesy of the mono-project   https   github com mono mono blob master mcs class System Web System Web HttpUtility cs     public static string JavaScriptStringEncode string value  bool addDoubleQuotes                if  string IsNullOrEmpty value               return addDoubleQuotes    quot   quot   quot  quot    string Empty           int len   value Length          bool needEncode   false          char c          for  int i   0  i  lt  len  i                          c   value i                if  c  gt   0  amp  amp  c  lt   31    c    34    c    39    c    60    c    62    c    92                                needEncode   true                  break                                   if   needEncode              return addDoubleQuotes    quot   quot  quot    value    quot   quot  quot    value           var sb   new System Text StringBuilder            if  addDoubleQuotes              sb Append   quot              for  int i   0  i  lt  len  i                          c   value i               if  c  gt   0  amp  amp  c  lt   7    c    11    c  gt   14  amp  amp  c  lt   31    c    39    c    60    c    62                  sb AppendFormat  quot   u 0 x4  quot    int c               else switch   int c                                        case 8                          sb Append  quot   b quot                            break                       case 9                          sb Append  quot   t quot                            break                       case 10                          sb Append  quot   n quot                            break                       case 12                          sb Append  quot   f quot                            break                       case 13                          sb Append  quot   r quot                            break                       case 34                          sb Append  quot     quot  quot                            break                       case 92                          sb Append  quot      quot                            break                       default                          sb Append c                           break                                       if  addDoubleQuotes              sb Append   quot              return sb ToString           This can be compacted into    https   github com mono mono blob master mcs class System Json System Json JsonValue cs public class SimpleJSON        private static  bool NeedEscape string src  int i                char c   src i           return c  lt  32    c      quot      c                        Broken lead surrogate                 c  gt     uD800   amp  amp  c  lt     uDBFF   amp  amp                   i    src Length - 1    src i   1   lt    uDC00     src i   1   gt    uDFFF                   Broken tail surrogate                 c  gt     uDC00   amp  amp  c  lt     uDFFF   amp  amp                   i    0    src i - 1   lt    uD800     src i - 1   gt    uDBFF                   To produce valid JavaScript                c      u2028     c      u2029                 Escape  quot  lt   quot  for  lt script gt  tags                 c         amp  amp  i  gt  0  amp  amp  src i - 1       lt                  public static string EscapeString string src                System Text StringBuilder sb   new System Text StringBuilder             int start   0          for  int i   0  i  lt  src Length  i                if  NeedEscape src  i                                 sb Append src  start  i - start                   switch  src i                                         case   b   sb Append  quot   b quot    break                      case   f   sb Append  quot   f quot    break                      case   n   sb Append  quot   n quot    break                      case   r   sb Append  quot   r quot    break                      case   t   sb Append  quot   t quot    break                      case    quot    sb Append  quot     quot  quot    break                      case       sb Append  quot      quot    break                      case      sb Append  quot     quot    break                      default                          sb Append  quot   u quot                            sb Append   int src i   ToString  quot x04 quot                             break                                    start   i   1                        sb Append src  start  src Length - start           return sb ToString

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I nice one-liner  used JsonConvert as others have but added substring to remove the added quotes and backslash    var escapedJsonString   JsonConvert ToString JsonString  Substring 1  JsonString Length - 2

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In  Net Core 3  and  Net 5   string escapedJsonString   JsonEncodedText Encode jsonString

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I have used following code to escape the string value for json  You need to add your     to the output of the following code   public static string EscapeStringValue string value        const char BACK SLASH             const char SLASH            const char DBL QUOTE             var output   new StringBuilder value Length       foreach  char c in value                switch  c                        case SLASH                  output AppendFormat   0  1    BACK SLASH  SLASH                   break               case BACK SLASH                  output AppendFormat   0  0    BACK SLASH                   break               case DBL QUOTE                  output AppendFormat   0  1   BACK SLASH DBL QUOTE                   break               default                  output Append c                   break                       return output ToString

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What about System Web Helpers Json Encode       see http   msdn microsoft com en-us library system web helpers json encode v vs 111  aspx

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String Format  X   c     That just outputs  X  Try this instead   string t     int c  ToString  X     sb Append    u    t PadLeft 4   0

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Yep  just add the following function to your Utils class or something       public static string cleanForJSON string s                if  s    null    s Length    0                return                        char         c     0           int          i          int          len   s Length          StringBuilder sb   new StringBuilder len   4           String       t           for  i   0  i  lt  len  i    1                c   s i               switch  c                    case                       case                          sb Append                            sb Append c                       break                  case                          sb Append                            sb Append c                       break                  case   b                       sb Append    b                        break                  case   t                       sb Append    t                        break                  case   n                       sb Append    n                        break                  case   f                       sb Append    f                        break                  case   r                       sb Append    r                        break                  default                      if  c  lt                                 t    000    String Format  X   c                           sb Append    u    t Substring t Length - 4                          else                           sb Append c                                             break                                  return sb ToString

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For those using the very popular Json Net project from Newtonsoft the task is trivial   using Newtonsoft Json        var s   JsonConvert ToString   a b    Console WriteLine s          This code prints    a  b   That is  the resulting string value contains the quotes as well as the escaped backslash

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I chose to use System Web Script Serialization JavaScriptSerializer  I have a small static helper class defined as follows  internal static partial class Serialization       static JavaScriptSerializer serializer           static Serialization                 serializer   new JavaScriptSerializer            serializer MaxJsonLength   Int32 MaxValue            public static string ToJSON lt T gt  T obj                return serializer Serialize obj             public static T FromJSON lt T gt  string data                if  Common IsEmpty data               return default T           else             return serializer Deserialize lt T gt  data            To serialize anything I just call Serialization ToJSON itemToSerialize  To deserialize I just call Serialization FromJSON lt T gt  jsonValueOfTypeT

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I use System Web HttpUtility JavaScriptStringEncode  string quoted   HttpUtility JavaScriptStringEncode input

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Building on the answer by Dejan  what you can do is import System Web Helpers  NET Framework assembly  then use the following function    static string EscapeForJson string s      string quoted   System Web Helpers Json Encode s     return quoted Substring 1  quoted Length - 2       The Substring call is required  since Encode automatically surrounds strings with double quotes

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I would also recommend using the JSON NET library mentioned  but if you have to escape unicode characters  e g   uXXXX format  in the resulting JSON string  you may have to do it yourself   Take a look at Converting Unicode strings to escaped ascii string for an example

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