C#將字符串格式化爲Json

private string ConvertStringToJson(string str)

        {

            //格式化json字符串

            JsonSerializer serializer =  new  JsonSerializer();

            TextReader tr =  new  StringReader(str);

            JsonTextReader jtr =  new  JsonTextReader(tr);

            object  obj = serializer.Deserialize(jtr);

            if  (obj !=  null )

            {

                StringWriter textWriter =  new  StringWriter();

                JsonTextWriter jsonWriter =  new  JsonTextWriter(textWriter)

                {

                    Formatting = Formatting.Indented,

                    Indentation = 4,

                    IndentChar =  ' '

                };

                serializer.Serialize(jsonWriter, obj);

                return  textWriter.ToString();

            }

            else

            {

                return  str;

            }         

        }