public class OracleDbContext : DbContext
{
    public string ConnectionString { get; set; }
    public OracleDbContext(string connectionString) => ConnectionString = connectionString;
    
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        var logger = new LoggerFactory();
        logger.AddConsole();
        logger.AddDebug();
        optionsBuilder.UseLoggerFactory(logger);
        optionsBuilder.UseOracle(ConnectionString);
        base.OnConfiguring(optionsBuilder);
    }
    
    public DbSet<User> User { get; set; }
    
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        // 這個方法是在Select完才由程式去轉換，不會影響到產出的SQL
        modelBuilder.Entity<User>()
            .Property(d => d.Name)
            .HasConversion(d => d.ToString(), d => Rawtohex(d));
        modelBuilder.Entity<User>()
            .Property(u => u.Type)
            .HasConversion(n => n.ToString(), n => TO_NUMBER(n));
        
        // 將table、column名稱改為大寫，以順利查到資料表 
        foreach (var entityType in modelBuilder.Model.GetEntityTypes())
        {
            entityType.Relational().TableName = entityType.Relational().TableName.ToUpper();
            foreach (var property in entityType.GetProperties())
                property.Relational().ColumnName = property.Relational().ColumnName.ToUpper();
        }
    }
    
    // DbFunction函式的內容實作無關結果，僅作為向EF註明說有這樣的函式
    [DbFunction]
    public static int TO_NUMBER(string str) => 0;
    
    [DbFunction]
    public static int TO_NUMBER(int i) => 0;
    
    [DbFunction]
    public static string Rawtohex(string str) => "";
}