dotnet core System.Text.Json unescape unicode string

Question

Using JsonSerializer.Serialize(obj) will produce an escaped string, but I want the unescaped version. For example:

using System;
using System.Text.Json;

public class Program
{
    public static void Main()
    {
        var a = new A{Name = "你好"};
        var s = JsonSerializer.Serialize(a);
        Console.WriteLine(s);
    }
}

class A {
    public string Name {get; set;}
}

will produce a string {"Name":"\u4F60\u597D"} but I want {"Name":"你好"}

I created a code snippet at https://dotnetfiddle.net/w73vnO
Please help me.

Answer 1

You need to set the JsonSerializer options not to encode those strings.

JsonSerializerOptions jso = new JsonSerializerOptions();
jso.Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping;

Then you pass this options when you call your Serialize method.

var s = JsonSerializer.Serialize(a, jso);        

Full code:

JsonSerializerOptions jso = new JsonSerializerOptions();
jso.Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping;

var a = new A { Name = "你好" };
var s = JsonSerializer.Serialize(a, jso);        
Console.WriteLine(s);

Result:

If you need to print the result in the console, you may need to install additional language. Please refer here.

Answer 2

To change the escaping behavior of the JsonSerializer you can pass in a custom JavascriptEncoder to the JsonSerializer by setting the Encoder property on the JsonSerializerOptions.

https://learn.microsoft.com/en-us/dotnet/api/system.text.json.jsonserializeroptions.encoder?view=netcore-3.0#System_Text_Json_JsonSerializerOptions_Encoder

The default behavior is designed with security in mind and the JsonSerializer over-escapes for defense-in-depth.

If all you are looking for is escaping certain "alphanumeric" characters of a specific non-latin language, I would recommend that you instead create a JavascriptEncoder using the Create factory method rather than using the UnsafeRelaxedJsonEscaping encoder.

JsonSerializerOptions options = new JsonSerializerOptions
{
    Encoder = JavaScriptEncoder.Create(UnicodeRanges.BasicLatin, UnicodeRanges.CjkUnifiedIdeographs)
};

var a = new A { Name = "你好" };
var s = JsonSerializer.Serialize(a, options);
Console.WriteLine(s);

Doing so keeps certain safe-guards, for instance, HTML-sensitive characters will continue to be escaped.

I would caution against using System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping flippantly since it does minimal escaping (which is why it has "unsafe" in the name). If the JSON you are creating is written to a UTF-8 encoded file on disk or if its part of web request which explicitly sets the charset to utf-8 (and is not going to potentially be embedded within an HTML component as is), then it is probably OK to use this.

See the remarks section within the API docs: https://learn.microsoft.com/en-us/dotnet/api/system.text.encodings.web.javascriptencoder.unsaferelaxedjsonescaping?view=netcore-3.0#remarks

You could also consider specifying UnicodeRanges.All if you expect/need all languages to remain un-escaped. This still escapes certain ASCII characters that are prone to security vulnerabilities.

JsonSerializerOptions options = new JsonSerializerOptions
{
    Encoder = JavaScriptEncoder.Create(UnicodeRanges.All)
};

For more information and code samples, see: https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-how-to?view=netcore-3.0#customize-character-encoding

See the Caution Note

Answer 3

Use:

JsonSerializerOptions options = new JsonSerializerOptions
{
    Encoder = JavaScriptEncoder.Create(UnicodeRanges.All)
};

Answer 4

You can use: System.Text.RegularExpressions.Regex.Unescape(string) to unescape the unicode characters. https://learn.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.unescape

Updating example from original question:

using System;
using System.Text.Json;

public class Program
{
    public static void Main()
    {
            var a = new A{Name = "你好"};
            var s = JsonSerializer.Serialize(a);
        
            var unescaped = System.Text.RegularExpressions.Regex.Unescape(s);

            Console.WriteLine(s);
            Console.WriteLine(unescaped);
        }
}

class A {
    public string Name {get; set;}
}

Output:

{"Name":"\u4F60\u597D"}
{"Name":"你好"}