using (var context = new SomeDbContext())
{
    context.Database.EnsureDeleted();
    context.Database.EnsureCreated();

    var terrains = new[] { Terrain.River, Terrain.Beach, Terrain.Park };
    var walksWithTerrain = await context.Walks
        .Where(e => terrains.Contains(e.Terrain))
        .ToListAsync();
}

public class DogWalk
{
    public int Id { get; set; }
    public Terrain Terrain { get; set; }
}

public enum Terrain
{
    Forest,
    River,
    Hills,
    Village,
    Park,
    Beach,
}

public class SomeDbContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer(@"Data Source=(LocalDb)\MSSQLLocalDB;Database=AllTogetherNow")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();

    public DbSet<DogWalk> Walks => Set<DogWalk>();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<DogWalk>().Property(e => e.Terrain).HasConversion<string>();
    }
}