Question

我有这种类的结构飞行
..OriginDestinations
.... FlightSegments

我的问题很简单，在lambda表达式中可以相同：

var result1 = (
    from sf in selectedFlights
    from odo in sf.OriginDestinationOptions
    from fs in odo.FlightSegments
    select new FlightNumberAndClass {
        FlightNumber = fs.FlightNumber,
        FlightClass = fs.FlightClass
    });

其中result1是IEnumerable<FlightNumberAndClass>

的类型

我尝试了这个但是：

var result2 =
    selectedFlights.Select(
        x => x.OriginDestinationOptions.Select(
            y =>
                y.FlightSegments.Select(
                    z => new FlightNumberAndClass {
                        FlightNumber = z.FlightNumber,
                        FlightClass = z.FlightClass
                    }
                    )
            )
        );

它给了我result2的类型“类似于” System.Linq.Enumerable.WhereSelectListIterator<IEnumerable<IEnumerable<FlightNumberAndClass>>>

Answer 1

SelectMany将序列的每个元素投影到IEnumerable<T>，并将生成的序列展平为一个序列。

IEnumerable<FlightNumberAndClass> result2 = selectedFlights
    .SelectMany(sf => sf.OriginDestinationOptions
        .SelectMany(odo => odo.FlightSegments
            .Select(fs => new FlightNumberAndClass 
                {
                    FlightNumber = fs.FlightNumber,
                    FlightClass = fs.FlightClass
                }
            )
        )
    );

Answer 2

在这种情况下，你可以像这个例子一样使用SelectMany：

List<List<List<string>>> list1 = new List<List<List<string>>>
            {
                new List<List<string>> {
                new List<string>{"a","b","c","d","e"},
                new List<string>{"a","b","c","d","e"},
                new List<string>{"a","b","c","d","e"}
                },
                new List<List<string>> {
                new List<string>{"a","b","c","d","e"},
                new List<string>{"a","b","c","d","e"},
                new List<string>{"a","b","c","d","e"}
                },
                new List<List<string>> {
                new List<string>{"a","b","c","d","e"},
                new List<string>{"a","b","c","d","e"},
                new List<string>{"a","b","c","d","e"}
                }
            };

            var result = list1.SelectMany(a => a.SelectMany(b => b.Select(c => c))).ToList();

Linq相当于lambda

2 个答案: