MyContext.cs

 public sealed class MyContext : DbContext
    {

        public DbSet<PostData> Posts { get; set; }
        public DbSet<VoteData> Votes { get; set; }

        public MyContext(DbContextOptions<MyContext> options) : base(options)
        {
        }

        public MyContext()
        {
            
        }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
                optionsBuilder.UseSqlite("Data Source = DataDb.db;");
            }
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfigurationsFromAssembly(typeof(MyContext).Assembly);
        }

        public class ContextBaseFactory : IDesignTimeDbContextFactory<MyContext>
        {
            public MyContext CreateDbContext(string[] args)
            {
                var optionsBuilder = new DbContextOptionsBuilder<MyContext>();

                if (!optionsBuilder.IsConfigured)
                {
                    optionsBuilder.UseSqlite("Data Source = DataDb.db;");
                }

                return new MyContext(optionsBuilder.Options);
            }
        }
    }