static IFreeSql fsql = new FreeSql.FreeSqlBuilder()
    .UseConnectionString(FreeSql.DataType.MySql, connectionString)
    //Automatically synchronize the entity structure to the database.
    .UseAutoSyncStructure(true) 
    //Be sure to define as singleton mode
    .Build(); 

using (var uow = fsql.CreateUnitOfWork())
{
  var songRepo = fsql.GetRepository<Song>();
  var userRepo = fsql.GetRepository<User>();
  songRepo.UnitOfWork = uow; //Manually bind unit of work
  userRepo.UnitOfWork = uow;
  songRepo.Insert(new Song());
  userRepo.Update(...);
  uow.Orm.Insert(new Song()).ExecuteAffrows();
  //Note: uow.Orm and fsql are both IFreeSql
  //uow.Orm CRUD and uow are the same transaction (understood as temporary IFreeSql)
  //fsql CRUD and uow are not in the same transaction
  uow.Commit();
}

public interface IUnitOfWork : IDisposable
{
  /// <summary>
  /// The object Select/Delete/Insert/Update/InsertOrUpdate is consistent with the unit of work transaction and can be omitted to pass WithTransaction
  /// </summary>
  IFreeSql Orm { get; }
  /// <summary>
  /// Open the transaction, or return to the opened transaction
  /// </summary>
  /// <param name="isCreate">If the transaction is not opened, then open</param>
  /// <returns></returns>
  DbTransaction GetOrBeginTransaction(bool isCreate = true);
  IsolationLevel? IsolationLevel { get; set; }
  void Commit();
  void Rollback();
  /// <summary>
  /// Entity change tracking within the unit of work
  /// </summary>
  DbContext.EntityChangeReport EntityChangeReport { get; }
}

fsql.SetDbContextOptions(opt => {
  opt.OnEntityChange = report => {
    Console.WriteLine(report);
  };
});

var uow = fsql.CreateUnitOfWork();
uow.OnEntityChange = report => {
  Console.WriteLine(report);
};

public class ChangeInfo {
  public object Object { get; set; }
  public EntityChangeType Type { get; set; }
  /// <summary>
  /// When Type = Update, get the object before the update
  /// </summary>
  public object BeforeObject { get; set; }
}
public enum EntityChangeType { Insert, Update, Delete, SqlRaw }

int Delete(Expression<Func<TEntity, bool>> predicate);