C# preserve escape sequence when reading JSON content using Json.NET

Question

C# preserve escape sequence when reading JSON content using Json.NET

Given the following json text content:

{ "Pattern": "[0-9]*\t[a-z]+" }

Which is reflected in a simple class:

public class Rule
{
    public string Pattern { get; set; }

    public bool Test(string text)
    {
        return new Regex(Pattern).IsMatch(text);
    }    
}

And it's deserialised like this:

var json = System.IO.File.ReadAllText("file.json");
var rule = JsonConvert.DeserializeObject<Rule>(text);

The value of Pattern is supposed to be a regex pattern. The problem is that, once the content is read, the " \\t " escape sequence is immediately applied as a escape character which is a tab, resulting in the string value: [0-9]* [az]+ .

What I understand is that the content is somewhat malformed, because it should look like this: [0-9]*\\\\t[az]+ to be valid within the Json content, escaping the backslash so it could be preserved and result into the actual pattern [0-9]*\\t[az]+ . But the file is user edited and I would just like to be able to loosely interpret the content, assuming that backslashes should be preserved (and escape sequences would not be transformed).

I tried to implement a custom JsonConverter but when looking up the token, the value is already resolved.

FIDDLE

Answer 1

I've tried the below code and it works...maybe i don't understand what is the problem or you can provide a sample that doesn't work with this:

StreamReader s= new StreamReader(@"test.txt");
string json = s.ReadToEnd();
json=json.Replace("\\","\\\\");
JObject obj = JObject.Parse(json);
string pattern = obj["Pattern"].ToString();
bool test = Regex.IsMatch("1    a", pattern);

test.txt contains just this:

{ "Pattern": "[0-9]*\t[a-z]+" }

Edit
As Thomasjaworsky remarks, instead of json=json.Replace("\\\\","\\\\\\\\"); is better to use Regex.Replace(json, @"(?<!\\\\)[\\\\](?!\\\\)", @"\\\\") , it will do the same replace, but only if not already escaped. Two backspaces in row are untouched.