How to create JSON string in C#

Question

I just used the XmlWriter to create some XML to send back in an HTTP response. How would you create a JSON string. I assume you would just use a stringbuilder to build the JSON string and them format your response as JSON?

Answer 1

This code snippet uses the DataContractJsonSerializer from System.Runtime.Serialization.Json in .NET 3.5.

public static string ToJson<T>(/* this */ T value, Encoding encoding)
{
    var serializer = new DataContractJsonSerializer(typeof(T));

    using (var stream = new MemoryStream())
    {
        using (var writer = JsonReaderWriterFactory.CreateJsonWriter(stream, encoding))
        {
            serializer.WriteObject(writer, value);
        }

        return encoding.GetString(stream.ToArray());
    }
}

Answer 2

The DataContractJSONSerializer will do everything for you with the same easy as the XMLSerializer. Its trivial to use this in a web app. If you are using WCF, you can specify its use with an attribute. The DataContractSerializer family is also very fast.

Answer 3

I've found that you don't need the serializer at all. If you return the object as a List. Let me use an example.

In our asmx we get the data using the variable we passed along

// return data
[WebMethod(CacheDuration = 180)]
public List<latlon> GetData(int id) 
{
    var data = from p in db.property 
               where p.id == id 
               select new latlon
               {
                   lat = p.lat,
                   lon = p.lon

               };
    return data.ToList();
}

public class latlon
{
    public string lat { get; set; }
    public string lon { get; set; }
}

Then using jquery we access the service, passing along that variable.

// get latlon
function getlatlon(propertyid) {
var mydata;

$.ajax({
    url: "getData.asmx/GetLatLon",
    type: "POST",
    data: "{'id': '" + propertyid + "'}",
    async: false,
    contentType: "application/json;",
    dataType: "json",
    success: function (data, textStatus, jqXHR) { //
        mydata = data;
    },
    error: function (xmlHttpRequest, textStatus, errorThrown) {
        console.log(xmlHttpRequest.responseText);
        console.log(textStatus);
        console.log(errorThrown);
    }
});
return mydata;
}

// call the function with your data
latlondata = getlatlon(id);

And we get our response.

{"d":[{"__type":"MapData+latlon","lat":"40.7031420","lon":"-80.6047970}]}

Answer 4

If you need complex result (embedded) create your own structure:

class templateRequest
{
    public String[] registration_ids;
    public Data data;
    public class Data
    {
        public String message;
        public String tickerText;
        public String contentTitle;
        public Data(String message, String tickerText, string contentTitle)
        {
            this.message = message;
            this.tickerText = tickerText;
            this.contentTitle = contentTitle;
        }                
    };
}

and then you can obtain JSON string with calling

List<String> ids = new List<string>() { "id1", "id2" };
templateRequest request = new templeteRequest();
request.registration_ids = ids.ToArray();
request.data = new templateRequest.Data("Your message", "Your ticker", "Your content");

string json = new JavaScriptSerializer().Serialize(request);

The result will be like this:

json = "{\"registration_ids\":[\"id1\",\"id2\"],\"data\":{\"message\":\"Your message\",\"tickerText\":\"Your ticket\",\"contentTitle\":\"Your content\"}}"

Hope it helps!

Answer 5

Take a look at http://www.codeplex.com/json/ for the json-net.aspx project. Why re-invent the wheel?

Answer 6

Using Newtonsoft.Json makes it really easier:

Product product = new Product();
product.Name = "Apple";
product.Expiry = new DateTime(2008, 12, 28);
product.Price = 3.99M;
product.Sizes = new string[] { "Small", "Medium", "Large" };

string json = JsonConvert.SerializeObject(product);

Documentation: Serializing and Deserializing JSON