Newtonsoft.Json.Linq.JObject clearly implements IEnumerable < T > , specifically IEnumerable < KeyValuePair < string, JToken > , after reading the metadata and source code, it is not explicitly implemented. It is said that objects of type JObject can directly call Select, Where and other linq extension methods, but the code is as follows:

using System.Linq;
...
var jobj = new JObject();
var xxx = jobj.Select(x=>x); //:JObjectSelect1JObjectSelect...
foreach(var x in jobj) { } //

I really don"t know any reason, so I ask for advice.