Convert JSON String to JSON Object c#

JObject defines method Parse for this:

JObject json = JObject.Parse(str);

You might want to refer to Json.NET documentation.

if you don't want or need a typed object try:

using Newtonsoft.Json;
// ...   
dynamic json  = JsonConvert.DeserializeObject(str);

or try for a typed object try:

Foo json  = JsonConvert.DeserializeObject<Foo>(str)

This works

    string str = "{ 'context_name': { 'lower_bound': 'value', 'pper_bound': 'value', 'values': [ 'value1', 'valueN' ] } }";
    JavaScriptSerializer j = new JavaScriptSerializer();
    object a = j.Deserialize(str, typeof(object));