CODEWITHSUNDEEP
c#jsonescaping
theringostarrs
theringostarrs

Reputation: 12410

How to escape JSON string?

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

Upvotes: 148

Views: 229677

Answers (17)

Stefan Steiger
Stefan Steiger

Reputation: 82406

2024 Update

In .NET Core, you can now do it like:

public static string JsonEncode(string input)
{
    string escaped = System.Text.Json.JsonEncodedText.Encode(input, System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping).Value;
    return escaped;
}

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 ? "\"\"" : string.Empty;

        int len = value.Length;
        bool needEncode = false;
        char c;
        for (int i = 0; i < len; i++)
        {
            c = value[i];

            if (c >= 0 && c <= 31 || c == 34 || c == 39 || c == 60 || c == 62 || c == 92)
            {
                needEncode = true;
                break;
            }
        }

        if (!needEncode)
            return addDoubleQuotes ? "\"" + value + "\"" : value;

        var sb = new System.Text.StringBuilder();
        if (addDoubleQuotes)
            sb.Append('"');

        for (int i = 0; i < len; i++)
        {
            c = value[i];
            if (c >= 0 && c <= 7 || c == 11 || c >= 14 && c <= 31 || c == 39 || c == 60 || c == 62)
                sb.AppendFormat("\\u{0:x4}", (int)c);
            else switch ((int)c)
                {
                    case 8:
                        sb.Append("\\b");
                        break;

                    case 9:
                        sb.Append("\\t");
                        break;

                    case 10:
                        sb.Append("\\n");
                        break;

                    case 12:
                        sb.Append("\\f");
                        break;

                    case 13:
                        sb.Append("\\r");
                        break;

                    case 34:
                        sb.Append("\\\"");
                        break;

                    case 92:
                        sb.Append("\\\\");
                        break;

                    default:
                        sb.Append(c);
                        break;
                }
        }

        if (addDoubleQuotes)
            sb.Append('"');

        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 < 32 || c == '"' || c == '\\'
            // Broken lead surrogate
            || (c >= '\uD800' && c <= '\uDBFF' &&
                (i == src.Length - 1 || src[i + 1] < '\uDC00' || src[i + 1] > '\uDFFF'))
            // Broken tail surrogate
            || (c >= '\uDC00' && c <= '\uDFFF' &&
                (i == 0 || src[i - 1] < '\uD800' || src[i - 1] > '\uDBFF'))
            // To produce valid JavaScript
            || c == '\u2028' || c == '\u2029'
            // Escape "</" for <script> tags
            || (c == '/' && i > 0 && src[i - 1] == '<');
    }



    public static string EscapeString(string src)
    {
        System.Text.StringBuilder sb = new System.Text.StringBuilder();

        int start = 0;
        for (int i = 0; i < src.Length; i++)
            if (NeedEscape(src, i))
            {
                sb.Append(src, start, i - start);
                switch (src[i])
                {
                    case '\b': sb.Append("\\b"); break;
                    case '\f': sb.Append("\\f"); break;
                    case '\n': sb.Append("\\n"); break;
                    case '\r': sb.Append("\\r"); break;
                    case '\t': sb.Append("\\t"); break;
                    case '\"': sb.Append("\\\""); break;
                    case '\\': sb.Append("\\\\"); break;
                    case '/': sb.Append("\\/"); break;
                    default:
                        sb.Append("\\u");
                        sb.Append(((int)src[i]).ToString("x04"));
                        break;
                }
                start = i + 1;
            }
        sb.Append(src, start, src.Length - start);
        return sb.ToString();
    }
}

Upvotes: 14

Alex from Jitbit
Alex from Jitbit

Reputation: 60942

None of the answers provided here worked for me because they were either encoding HTML-characters (like ampersand, single-quotes or triangle brackets were encoded as \u003c for example, but it's perfectly fine valid JSON) or used external dependencies (like NewtonSoft) or were manual coding.

So here's a modern one-liner answer for .NET Core from 2024

using System.Text.Json;
using System.Text.Encodings.Web;

string escaped = JsonEncodedText.Encode(input, JavaScriptEncoder.UnsafeRelaxedJsonEscaping).Value;
//this is important ---------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Enjoy.

Upvotes: 1

veni
veni

Reputation: 317

The C# method bellow is a more advanced optimization version using Span for small string inputs, to avoid heap allocation and StringBuilder for larger inputs to avoids excessive stack usage.

        public static string EscapeJsonText(string text) {
        if (string.IsNullOrEmpty(text)) return string.Empty;
        
        if (text.Length <= 256) {
            int count = 0;
            foreach (char c in text) {
                switch (c) {
                case '\\':
                case '\"':
                case '\b':
                case '\f':
                case '\n':
                case '\r':
                case '\t':
                    count += 2;
                    break;

                default:
                    count++;
                    break;
                }
            }

            Span<char> result = stackalloc char[count];
            count = 0;
            foreach (char c in text) {
                switch (c) {
                case '\\':
                case '\"':
                    result[count++] = '\\';
                    result[count++] = c;
                    break;

                case '\b':
                    result[count++] = '\\';
                    result[count++] = 'b';
                    break;

                case '\f':
                    result[count++] = '\\';
                    result[count++] = 'f';
                    break;

                case '\t':
                    result[count++] = '\\';
                    result[count++] = 't';
                    break;

                case '\n':
                    result[count++] = '\\';
                    result[count++] = 'n';
                    break;

                case '\r':
                    result[count++] = '\\';
                    result[count++] = 'r';
                    break;

                default:
                    result[count++] = c;
                    break;
                }
            }

            return result.ToString();
        }

        StringBuilder builder = new StringBuilder();
        foreach (char c in text) {
            switch (c) {
            case '\\': builder.Append("\\\\"); break;
            case '\"': builder.Append("\\\""); break;
            case '\b': builder.Append("\\b"); break;
            case '\f': builder.Append("\\f"); break;
            case '\n': builder.Append("\\n"); break;
            case '\r': builder.Append("\\r"); break;
            case '\t': builder.Append("\\t"); break;
            default: builder.Append(c); break;
            }
        }
        return builder.ToString();
    }

Upvotes: 0

Pravin Chandankhede
Pravin Chandankhede

Reputation: 116

.NET 6 - System.Text.Json

var encodedText = JsonEncodedText.Encode(inputText);

Upvotes: 1

AnthonyVO
AnthonyVO

Reputation: 3983

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<T>(T obj)
    {
        return serializer.Serialize(obj);
    }
    public static T FromJSON<T>(string data)
    {
        if (Common.IsEmpty(data))
            return default(T);
        else
            return serializer.Deserialize<T>(data);
    }
}

To serialize anything I just call Serialization.ToJSON(itemToSerialize)

To deserialize I just call Serialization.FromJSON<T>(jsonValueOfTypeT)

Upvotes: 0

Jawad Al Shaikh
Jawad Al Shaikh

Reputation: 2735

In .Net Core 3+ and .Net 5+:

string escapedJsonString = JsonEncodedText.Encode(jsonString);

Upvotes: 16

Joshua Duxbury
Joshua Duxbury

Reputation: 5260

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);

Upvotes: 4

Dror Harari
Dror Harari

Reputation: 3317

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.

Upvotes: 84

Rok Strniša
Rok Strniša

Reputation: 7222

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.

Upvotes: 41

xmedeko
xmedeko

Reputation: 7820

I use System.Web.HttpUtility.JavaScriptStringEncode

string quoted = HttpUtility.JavaScriptStringEncode(input);

Upvotes: 117

innominate227
innominate227

Reputation: 11731

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<string,List<long>>();

        for (var n = 0; n < 10; n++)
        {
            var count = 1000 * 1000;

            var sw = Stopwatch.StartNew();
            for (var i = 0; i < 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 < 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 < 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 < 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();
}

Upvotes: 5

Dejan
Dejan

Reputation: 10373

What about System.Web.Helpers.Json.Encode(...) (see http://msdn.microsoft.com/en-us/library/system.web.helpers.json.encode(v=vs.111).aspx)?

Upvotes: 3

user2058470
user2058470

Reputation: 21

String.Format("X", c);

That just outputs: X

Try this instead:

string t = ((int)c).ToString("X");

sb.Append("\\u" + t.PadLeft(4, '0'));

Upvotes: 2

Amit Bhagat
Amit Bhagat

Reputation: 4300

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();
}

Upvotes: 15

Clive Paterson
Clive Paterson

Reputation: 789

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 < 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 < ' ') {
                        t = "000" + String.Format("X", c);
                        sb.Append("\\u" + t.Substring(t.Length - 4));
                    } else {
                        sb.Append(c);
                    }
                    break;
            }
        }
        return sb.ToString();
    }

Upvotes: 36

Kevin Hakanson
Kevin Hakanson

Reputation: 42240

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.

Upvotes: 4

Jim Schubert
Jim Schubert

Reputation: 20367

There's a Json library at Codeplex

Upvotes: 0

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