EntityFramework Core dbContext doesn't recognize SaveChanges() [closed]

Question

I am working on .NET CORE 6 App along with Entity Framework CORE. I have created DbContext class that I am reference in my abstract BaseCommand Class. The script to create record inherited from BaseCommand class and hence got reference to dbContext. I am not able to recognise SaveChanges and need help based on current implementation

DbContext

public class AppDbContext : DbContext, IAppDbContext
{
    public AppDbContext(DbContextOptions<AppDbContext> options)
        : base(options) { }

    public virtual DbSet<Customer> Customers { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.ApplyConfiguration(new CustomerConfiguration());
    }
}

BaseCommand

public abstract class BaseCommand<TResult>
{
    protected IAppDbContext db { get; }

    protected BaseCommand(IAppDbContext dbContext)
    {
        this.db = dbContext;
    }

    public abstract TResult Execute();
}

Create Customer Class

using Microsoft.EntityFrameworkCore;

public class CreateCustomerCommand : BaseCommand<Customer>, ICreateCustomerCommand
{
    public CreateCustomerCommand(IAppDbContext dbContext) 
        : base(dbContext)
    {
    }

    public CustomerDto CustomerDtoObject { get; set; }

    public override Customer Execute()
    {
        if(CustomerDtoObject != null)
        {
                var customer = new Customer
                {
                    Name = CustomerDtoObject.Name,
                    Email = CustomerDtoObject.Email,
                    Address = CustomerDtoObject.Address,
                };

                db.Customers.Add(customer);
                db.SaveChanges(); // not recognised need help here?
        }
    }
}

IAppDbContext

public interface IAppDbContext
{
    int SaveChanges();
    DatabaseFacade Database { get; }

    DbSet<Customer> Customers { get; set; }

}