using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace DataModel
{
    public class Note : INotifyPropertyChanged
    {
        string header;
        string text;
        public string NoteHeader
        {
            get { return header; }
            set
            {
                header = value;
                OnPropertyChanged();
            }
        }

        public string NoteText
        {
            get { return text; }
            set
            {
                text = value;
                OnPropertyChanged();
            }
        }
        public int NoteId { get; set; }
        public bool Pin { get; set; }


        public int UserId { get; set; }
        public virtual User User { get; set; }


        public event PropertyChangedEventHandler PropertyChanged;
        void OnPropertyChanged([CallerMemberName]string propertyName = "")
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace Project.ViewModels

public static string adress = "http://REAL:IP/";
public static string  Key = "KEY";

public static ObservableCollection<Note> GetNotes() //Коллекция заметок
                {
                     HttpClient client = new HttpClient();
                     client.BaseAddress = new Uri(adress);
                     var json = client.GetStringAsync($"api/notes");
                     ObservableCollection<Note> notes = JsonConvert.DeserializeObject<ObservableCollection<Note>>(json.Result);

                    ObservableCollection<Note> notedecrypted = notes;
                    //Расшифровываем заголовок

                    var x = notes.NoteHeader;
                    var decryptedheader = Decrypt(x, Key);
                    notedecrypted.NoteHeader = decryptedheader;

                    //Расшифровываем текст
                    var z = notes.NoteText;
                    var decryptedtext = Decrypt(z, Key);
                    notedecrypted.NoteText = decryptedtext;


                    return notedecrypted;
                }