C# SelectMany 错误“无法将类型 'System.Collections.Generic.List<char>' 隐式转换为 'System.Collections.Generic.List<List>'”

Question

linq 内部 Select 我有一个 SelectMany 抛出错误

C# SelectMany error " Cannot Implicitly convert type 'System.Collections.Generic.List<char>' to 'System.Collections.Generic.List<List>' "

List<Hotel> hotelList = reservations
    .GroupBy(i => i.hotelID)
    .Select(c => new Hotel()
    {
        HotelID = c.First().HotelID,
        HotelName = c.First().HotelName,
        HotelAddress1 = c.First().HotelAddress1,
        HotelAddress2 = c.First().HotelAddress2,
        HotelAddress3 = c.First().HotelAddress3,
        HotelCity = c.First().CCCity,
        HotelPostalCode = c.First().CCZip,
        ReservationNumbers = c.SelectMany( i => i.ReservationNumber).Distinct().ToList()

    }).ToList();

SelectMany 自动将其转换为 IEnumerable<char>，然后 ToList 将其转换为 List<Char>

i.ReservationNumber是String类型，ReservationNumbers是List<string>类型，c是IGrouping<Reservation, int>[=33=类型]

强制转换为 List<string> 或如何将 SelectMany 转换为 return 的方法是什么 IEnumerable<string>

Answer 1

如果i.ReservationNumber的类型是String，则只需写成

ReservationNumbers = c.Select( i => i.ReservationNumber).Distinct().ToList()

SelectMany 尝试遍历 ReservationNumber 的元素，String 是 IEnumerable<char>

C# SelectMany 错误“无法将类型 'System.Collections.Generic.List<char>' 隐式转换为 'System.Collections.Generic.List<List>'”

C# SelectMany error " Cannot Implicitly convert type 'System.Collections.Generic.List<char>' to 'System.Collections.Generic.List<List>' "

c#

linq

ienumerable

types

list