C#文本转换为Json格式

private string ConvertJsonString(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;

           }         

       }