Entity Framework

The Iban type can be used in your domain and easily persisted in a varchar(34) field with Entity Framework using a value converter.

The maximum length of any IBAN in electronic format is 34 characters. The actual length varies by country.

Your entity configuration on a typical SQL database would look something like this:

public record Account(Iban BankAccountNumber);

public class MyDbContext : DbContext
{
    private IIbanParser _ibanParser;

    public MyDbContext(IIbanParser ibanParser)
    {
        _ibanParser = ibanParser;
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        var accountType = modelBuilder.Entity<Account>();

        accountType
            .Property(e => e.BankAccountNumber)
            .HasColumnType("varchar(34)")
            .HasConversion(
                iban => iban.ToString(IbanFormat.Electronic),
                ibanStr => _ibanParser.Parse(ibanStr)
            );
    }
}

For more information: https://learn.microsoft.com/en-us/ef/core/modeling/value-conversions