using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var jsonStr = @"{ ""files"": [

          {

            ""filename"": ""892a3a3bb7814d67995d4059b278c581.png"",

            ""real_filename"": ""Logo - Trimmed.png"",

            ""filesize"": 42198,

            ""filetype"": ""image/png"",

            ""file"": ""xxxx""

           },

           {

            ""filename"": ""22a3a3bb7814d67995d4059b278c581.png"",

            ""real_filename"": ""Logo - Trimmed2.png"",

            ""filesize"": 42198,

            ""filetype"": ""image/png"",

            ""file"": ""xxxx""

           }

        ] }";

        var jObj = JObject.Parse(jsonStr);

        foreach (JObject obj in jObj["files"] as JArray)

        {

            obj.Remove("file");

        }

        Console.WriteLine(JsonConvert.SerializeObject(jObj, new JsonSerializerSettings

                                                      {

                                                        Formatting = Formatting.Indented  

                                                      }));

    }

}