private ISelect <T> MakeLink(Action <SelectImpl <T> > func)
{
//构造新链，传递给下一个
SelectImpl <T> sel = new SelectImpl <T>(this);
func.Invoke(sel);
return(sel);
}
private SelectImpl(SelectImpl <T> obj) : base(obj._link_list)
{
this._select_cols = obj._select_cols;
this._top_sql = obj._top_sql;
this._count_sql = obj._count_sql;
this._discint_sql = obj._discint_sql;
if (this._link_list.FirstOrDefault(f => f is ISelect <T>) is ISelect <T> _sel)
{
this._link_list.Remove(_sel);
}
this._link_list.Add(this);
}