LINQ 选择嵌套列表上的表达式

Question

How would I go about looping through a nested list with Linq?

I have a nested list which looks like this:

var bookings = new List<List<Booking>>();

Inside the Booking class are booking details, and such

I want to loop through each indivudal list and extract the list which is nested by using Linq, but I'm struggling to do it :(

I'm not sure what method i should use with Linq, i've tried using SelectMany but i dont think I understand it well enough.

Answer 1

If you're trying to flatten the list with SelectMany :

bookings.SelectMany((list) => list);

If you're trying to extract each individual list:

bookings.ForEach((list) => {
    // Do something with the nested list
});

If you're trying to filter the nested lists, but maintain those the lists:

bookings.Select((list) => list.Where((item) => item.Price > 20));

And so on.

SelectMany expects a function that turns each item in a list into a IEnumerable<T> and then flattens the resulting IEnumerable<T> of IEnumerable<T> s into a IEnumerable<T> . By using SelectMany with an identity function (list) => list you're effectively doing nothing with each item in the list—they are already IEnumerable<T>'s and, as such, dont need any further transformation— SelectMany will then subsequently flatten the resulting IEnumerable<T> of IEnumerable<T> s.