How to get values from IGrouping

Question

I have a question about IGrouping and Select() method.

Lets say I've got IEnumerable<IGrouping<int, smth>> in this way:

var groups = list.GroupBy(x => x.ID);

where list is a List<smth>.

And now I need to pass values of each IGrouping to another list in some way.:

foreach (var v in structure)
{
    v.ListOfSmth = groups.Select(...); // <- ???
}

---

Can anybody suggest how to get values (List<smth>) from IGrouping<int, smth> in such context?

Answer 1

Since IGrouping<TKey, TElement> implements IEnumerable<TElement>, you can use SelectMany to put all the IEnumerables back into one IEnumerable all together:

List<smth> list = new List<smth>();
IEnumerable<IGrouping<int, smth>> groups = list.GroupBy(x => x.id);
IEnumerable<smth> smths = groups.SelectMany(group => group);
List<smth> newList = smths.ToList();

Answer 2

foreach (var v in structure) 
{     
    var group = groups.Single(g => g.Key == v. ??? );
    v.ListOfSmth = group.ToList();
}

---

First you need to select the desired group. Then you can use the ToList method of on the group. The IGrouping is a IEnumerable of the values.

Answer 3

From definition of IGrouping :

IGrouping<out TKey, out TElement> : IEnumerable<TElement>, IEnumerable

you can just iterate through elements like this:

IEnumerable<IGrouping<int, smth>> groups = list.GroupBy(x => x.ID)
foreach(IEnumerable<smth> element in groups)
{
//do something
}

Answer 4

More clarified version of above answers:

IEnumerable<IGrouping<int, ClassA>> groups = list.GroupBy(x => x.PropertyIntOfClassA);

foreach (var groupingByClassA in groups)
{
    int propertyIntOfClassA = groupingByClassA.Key;

    //iterating through values
    foreach (var classA in groupingByClassA)
    {
        int key = classA.PropertyIntOfClassA;
    }
}