How to create JSON string in C#

You could use the JavaScriptSerializer class, check this article to build an useful extension method.

Code from article:

namespace ExtensionMethods
{
    public static class JSONHelper
    {
        public static string ToJSON(this object obj)
        {
            JavaScriptSerializer serializer = new JavaScriptSerializer();
            return serializer.Serialize(obj);
        }

        public static string ToJSON(this object obj, int recursionDepth)
        {
            JavaScriptSerializer serializer = new JavaScriptSerializer();
            serializer.RecursionLimit = recursionDepth;
            return serializer.Serialize(obj);
        }
    }
}

Usage:

using ExtensionMethods;

...

List<Person> people = new List<Person>{
                   new Person{ID = 1, FirstName = "Scott", LastName = "Gurthie"},
                   new Person{ID = 2, FirstName = "Bill", LastName = "Gates"}
                   };


string jsonString = people.ToJSON();

Simlpe use of Newtonsoft.Json and Newtonsoft.Json.Linq libraries.

        //Create my object
        var myData = new
        {
            Host = @"sftp.myhost.gr",
            UserName = "my_username",
            Password = "my_password",
            SourceDir = "/export/zip/mypath/",
            FileName = "my_file.zip"
        };

        //Tranform it to Json object
        string jsonData = JsonConvert.SerializeObject(myData);

        //Print the Json object
        Console.WriteLine(jsonData);

        //Parse the json object
        JObject jsonObject = JObject.Parse(jsonData);

        //Print the parsed Json object
        Console.WriteLine((string)jsonObject["Host"]);
        Console.WriteLine((string)jsonObject["UserName"]);
        Console.WriteLine((string)jsonObject["Password"]);
        Console.WriteLine((string)jsonObject["SourceDir"]);
        Console.WriteLine((string)jsonObject["FileName"]);

This library is very good for JSON from C#

http://james.newtonking.com/pages/json-net.aspx

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());
    }
}

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

If you can't or don't want to use the two built-in JSON serializers (JavaScriptSerializer and DataContractJsonSerializer) you can try the JsonExSerializer library - I use it in a number of projects and works quite well.

If you want to avoid creating a class and create JSON then Create a dynamic Object and Serialize Object.

            dynamic data = new ExpandoObject();
            data.name = "kushal";
            data.isActive = true;

            // convert to JSON
            string json = Newtonsoft.Json.JsonConvert.SerializeObject(data);

Read the JSON and deserialize like this:

            // convert back to Object
            dynamic output = Newtonsoft.Json.JsonConvert.DeserializeObject(json);

            // read a particular value:
            output.name.Value

ExpandoObject is from System.Dynamic namespace.

If you're trying to create a web service to serve data over JSON to a web page, consider using the ASP.NET Ajax toolkit:

http://www.asp.net/learn/ajax/tutorial-05-cs.aspx

It will automatically convert your objects served over a webservice to json, and create the proxy class that you can use to connect to it.

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.

Include:

using System.Text.Json;

Then serialize your object_to_serialize like this: JsonSerializer.Serialize(object_to_serialize)