CODEWITHSUNDEEP
c#linqlist
Dries
Dries

Reputation: 1005

Split a list in multiple lists per value of a certain property

I have a list of data structures that have a property called group. Now, I would like to split this list in multiple lists per group-value. For example, I have 5 objects in the original list with the following group-values:

0. group: "group1"
1. group: "group1"
2. group: "group2"
3. group: "group2"
4. group: "group3"

Keeping that list in mind I would like 3 lists coming out of this per group-value. One list will only have objects with group "group1", the next one "group2" and so on...

I guess I can do this with Linq (I can do this to get a single list from a group with a given value) but I can't figure out how to do it automatically with all possible groups.

Upvotes: 4

Views: 3711

Answers (3)

Ugur Basak
Ugur Basak

Reputation: 317

You can use group be feature of Linq. I'm adding a sample, the output will be.

  • Group group1 has 2 elements
  • Group group2 has 2 elements

  • Group group3 has 1 elements

    List<GroupTemp> list = new List<GroupTemp>();
list.Add(new GroupTemp("group1", "1"));
list.Add(new GroupTemp("group1", "2"));
list.Add(new GroupTemp("group2", "3"));
list.Add(new GroupTemp("group2", "4"));
list.Add(new GroupTemp("group3", "5"));

var groupedList = list.GroupBy(t => t.key).ToList();

foreach (var entity in groupedList)
{
    Console.WriteLine(String.Format("Group {0} has {1} elements", entity.Key, entity.Count()));
}

Upvotes: 0

Diego
Diego

Reputation: 16714

GroupBy does what you are looking for. But if you want the results in a list containing one list per group, you should use it like this:

IList<List<Item>> groups = items.GroupBy(x => x.Group).Select(x => x.ToList()).ToList();

Upvotes: 4

mstaessen
mstaessen

Reputation: 1317

Assuming you have multiple types in the same collection, I think you should introduce an interface (name is up for debate ;))

public interface IHaveGroup 
{
    string Group { get; }
}

Then, you can just use LINQ.

IEnumerable<IHaveGroup> items = // get all items as a single group
var groups = items.GroupBy(x => x.Group);

Upvotes: 3

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