DiscordClient/DiscordDelete/DiscordContext.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

namespace DiscordDelete
{
    public class DiscordContext : DbContext
    {
        private const string DataPath = "messages.db";
        public DbSet<Message> Messages { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) =>
            optionsBuilder.UseSqlite($"Data Source={DataPath}");

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Message>().HasIndex(m => m.MessageId).IsUnique(true);
            base.OnModelCreating(modelBuilder);
        }
    }

    public class Message
    {
        [Key]
        public long Id { get; set; }
        public string? ChannelId { get; set; }
        public string? MessageId { get; set; }
        public string? Content { get; set; }
        public int? LastHttpCode { get; set; }
    }
}