Querying JSON Nested Arrays with Linq, JSON.NET, C#

Question

This post is an effort to ask a more direct question related to my other recent post (Picking Out Simple Properties from Hierarchical JSON Part II):

Given nested JSO

Answer 1

How about something like this:

List<JObject> list = 
    JObject.Parse(json)
           .Descendants()
           .Where(jt => jt.Type == JTokenType.Property && ((JProperty)jt).Value.HasValues)
           .Cast<JProperty>()
           .Select(prop =>
           {
               var obj = new JObject(new JProperty("Name", prop.Name));
               if (prop.Value.Type == JTokenType.Array)
               {
                   var items = prop.Value.Children<JObject>()
                                         .SelectMany(jo => jo.Properties())
                                         .Where(jp => jp.Value.Type == JTokenType.String);
                   obj.Add(items);
               }
               var parentName = prop.Ancestors()
                                    .Where(jt => jt.Type == JTokenType.Property)
                                    .Select(jt => ((JProperty)jt).Name)
                                    .FirstOrDefault();
               obj.Add("Parent", parentName ?? "");
               return obj;
           })
           .ToList();

Fiddle: https://dotnetfiddle.net/FMxzls

If you're not that familiar with LINQ-to-JSON, here's how it breaks down:

1. Parse the json string into a JObject

   JObject.Parse(json)
   

2. From that JObject, get all of its descendant JTokens

          .Descendants()
   

3. Filter that list to only JProperties whose values have children

          .Where(jt => jt.Type == JTokenType.Property && ((JProperty)jt).Value.HasValues)
   

4. Cast the JTokens to JProperties to make them easier to work with in the next step

          .Cast<JProperty>()
   

5. Now, for each JProperty we selected, transform it as follows:

          .Select(prop =>
          {
   

6. Create a new JObject and add the JProperty's name as the Name property of the new object

              var obj = new JObject(new JProperty("Name", prop.Name));
   

7. If the value of the JProperty is an array...

              if (prop.Value.Type == JTokenType.Array)
              {
   

8. Get all the direct children of the array which are JObjects

                  var items = prop.Value.Children<JObject>()
   

9. From those JObjects, get all the JProperties

                                        .SelectMany(jo => jo.Properties())
   

10. Filter those JProperties to include only the ones whose values are strings)

                                         .Where(jp => jp.Value.Type == JTokenType.String);
    

11. Add these item JProperties to the new JObject we created earlier

                    obj.Add(items);
                }
    

12. Next, find the first ancestor JProperty of the current JProperty and get its name

                var parentName = prop.Ancestors()
                                     .Where(jt => jt.Type == JTokenType.Property)
                                     .Select(jt => ((JProperty)jt).Name)
                                     .FirstOrDefault();
    

13. Add the parent name to the JObject we're are building; use an empty string if there was no parent

                obj.Add("Parent", parentName ?? "");
    

14. Continue with the next transform

                return obj;
            })
    

15. Lastly put all the JObjects we built into a list.

            .ToList();