DbContext.cs

public class MyDbContext : DbContext
{
    public Guid TenantId { get; }
    public string Connection { get; }
    public DbSet<Customer> Customers { get; set; }

    public MyDbContext(Guid tenantId, string connection)
    {
        TenantId = tenantId;
        Connection = connection;

        this.Filter<Customer>(x => x.Where(q => q.TenantId == TenantId));
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(Connection);
    }
}