I used a normal query inside a foreach
to reach my goal, but I think there is a better way.
int max = 0;
foreach(Area area in myZoo.AreaList)
{
max = (from a in area.AnimalList
select a.ID).Max();
}
return max;
How can I use a pure LINQ to get the max
of all sublists? ( Animal
is a List
of the class Animal
inside the AreaList
and contains an Int32
called ID
) Erm, and Lambda is welcome, so don't hastitate to answer only because you only know the lambda answer ;)
public class Zoo
{
public List<Area> AreaList {get; set;}
}
public class Area
{
public List<Animal> AnimalList {get; set;}
}
public class Animal
{
public List<int> Id {get; set;}
}
Only the short form so no one gets confused ;)
Although SelectMany
works, I feel query is more readable in such case.
var max = (from area in myZoo.AreaList
from animal in area.AnimalList
from id in animal.Id
select id).Max();
You are looking for a nested SelectMany
.
SelectMany
will return a single IEnumerable<T>
from the many "inner" Ienumerable<T>
- so Zoo.SelectMany(a => a.AreaList)
will return a single IEnumerable<Area>
containing all the IEnumerable<Area>
from the Area
property - then you do it one more time for the List<Animal>
in the Area
class:
Sample data:
var zoo = new Zoo() {
AreaList = new List<Area>()
{
new Area()
{
AnimalList = new List<Animal>()
{
new Animal() {Id = new List<int>() {1, 2, 3}},
new Animal() {Id = new List<int>() {4, 5, 6}}
}
},
new Area()
{
AnimalList = new List<Animal>()
{
new Animal() {Id = new List<int>() {7, 8, 9}},
new Animal() {Id = new List<int>() {10, 11}}
}
},
}
};
Linq query:
var max = zoo.AreaList.SelectMany(a => a.AnimalList).SelectMany(a => a.Id).Max();
Console.WriteLine(max);
Result: 11
In query syntax you can do SelectMany
by chaining from
clauses, as shown in gxp's answer. (Personally, I prefer the method chaining syntax, so it took me some time to figure that one out...)
var max = zoo.AreaList.Max(arl => arl.AnimalList.Max(anl => anl.Id)).Max();
The maximum value of all maximum values of all AnimalLists
, and the Max of them.
That's effectievly the same as ZoharPeled's SelectMany
, except he flattens the list and takes the max of all items where I take the max of each list again and again.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.