C# - parsing json formatted data into nested hashtables

Question

I’m trying to work with some json formatted data in C#, but, I’m having some problems determining the proper way to approach the problem. My issue is that the json formatted data will be in an unknown format (I know that sounds odd … please read on). Basically, the json formatted data will be some collection of name/value pairs where the values may or may not be arrays of nested name/value pairs. To make things more fun, the nesting of the name/value pair arrays can continue on ad infinitum.

For example: I might have some data that looks like…

{
    "1": {
        "1.1": {
            "1.1.1": "value1",
            "1.1.2": "value2",
            "1.1.3": "value3"
        },
        "1.2": "value4",
        "1.3": {
            "1.3.1": {
                "1.3.1.1": "value5",
                "1.3.1.2": "value6"
            },
            "1.3.1.2": "value7",
            "1.3.1.3": "value8"
        }
    }
}

Unfortunately, I don’t know how much nesting is going to occur and technically I don’t know what names/value pairs will be present in any given message.

Is there any supported mechanism in C# that would enable me to easily parse this into a nested set of hastables?

I’d like to do something along the lines of (note this code is not 100% syntactically correct and would better be done via recursion … but it get’s the idea across).

Hashtable ht = [deserialize data method](jsonformattedstring);
foreach (Hashtable nested in ht)
{
    If (nested.count > 1)
        {
        Foreach (hashtable next in nested)
        …
        }
}

Answer 1

I didn't like the .Net Json parsing...it does some strange things occasionally. I've switched to Json.NET, an open source library. It has a nice JObject object that will do what you need.

Answer 2

In .NET, you have the JsonArray, which allows you to load up and parse the JSON data. It creates an array of JsonValue and it is completely nested based on the JSON data it parses.

If you specifically need Hashtable, you could translate the data from JsonArray, though Hastable is all but deprecated in favor of Dictionary.

Josh Holmes has a pretty good "getting started" post about JSON in .NET: http://www.joshholmes.com/blog/2009/01/20/PlayingWithJSON.aspx

Answer 3

You may want to look at http://techblog.procurios.nl/k/n618/news/view/14605/14863/How-do-I-write-my-own-parser-for-JSON.html It is a simple library that parses a JSON string into Hashtables and ArrayLists. It can also turn these structures into JSON again.

Answer 4

Here is a method I wrote in C# to parse JSON and return a dictionary. Of course it is not appropriate for all use cases, but something like this will give you a nice one-pass parse of the JSON:

/*
     * This method takes in JSON in the form returned by javascript's
     * JSON.stringify(Object) and returns a string->string dictionary.
     * This method may be of use when the format of the json is unknown.
     * You can modify the delimiters, etc pretty easily in the source
     * (sorry I didn't abstract it--I have a very specific use).
     */ 
    public static Dictionary<string, string> jsonParse(string rawjson)
    {
        Dictionary<string, string> outdict = new Dictionary<string, string>();
        StringBuilder keybufferbuilder = new StringBuilder();
        StringBuilder valuebufferbuilder = new StringBuilder();
        StringReader bufferreader = new StringReader(rawjson);

        int s = 0;
        bool reading = false;
        bool inside_string = false;
        bool reading_value = false;
        //break at end (returns -1)
        while (s >= 0)
        {
            s = bufferreader.Read();
            //opening of json
            if (!reading)
            {
                if ((char)s == '{' && !inside_string && !reading) reading = true;
                continue;
            }
            else
            {
                //if we find a quote and we are not yet inside a string, advance and get inside
                if (!inside_string)
                {
                    //read past the quote
                    if ((char)s == '\"') inside_string = true;
                    continue;
                }
                if (inside_string)
                {
                    //if we reached the end of the string
                    if ((char)s == '\"')
                    {
                        inside_string = false;
                        s = bufferreader.Read(); //advance pointer
                        if ((char)s == ':')
                        {
                            reading_value = true;
                            continue;
                        }
                        if (reading_value && (char)s == ',')
                        {
                            //we know we just ended the line, so put itin our dictionary
                            if (!outdict.ContainsKey(keybufferbuilder.ToString())) outdict.Add(keybufferbuilder.ToString(), valuebufferbuilder.ToString());
                            //and clear the buffers
                            keybufferbuilder.Clear();
                            valuebufferbuilder.Clear();
                            reading_value = false;
                        }
                        if (reading_value && (char)s == '}')
                        {
                            //we know we just ended the line, so put itin our dictionary
                            if (!outdict.ContainsKey(keybufferbuilder.ToString())) outdict.Add(keybufferbuilder.ToString(), valuebufferbuilder.ToString());
                            //and clear the buffers
                            keybufferbuilder.Clear();
                            valuebufferbuilder.Clear();
                            reading_value = false;
                            reading = false;
                            break;
                        }
                    }
                    else
                    {
                        if (reading_value)
                        {
                            valuebufferbuilder.Append((char)s);
                            continue;
                        }
                        else
                        {
                            keybufferbuilder.Append((char)s);
                            continue;
                        }
                    }
                }
                else
                {
                    switch ((char)s)
                    {
                        case ':':
                            reading_value = true;
                            break;
                        default:
                            if (reading_value)
                            {
                                valuebufferbuilder.Append((char)s);
                            }
                            else
                            {
                                keybufferbuilder.Append((char)s);
                            }
                            break;
                    }
                }
            }
        }
        return outdict;
    }