Linq Multiple Group by in a List<T> Then Convert to List<T>

LINQ Multiple Group By in a List<T> then convert to List<T>

I think you're after something like this...

List<Person> persons = new List<Person>
{
    new Person()
    {
        ID = "1",
        Name = "Joe",
        District = "Columbia",
        Level = "10"
    },
    new Person()
    {
        ID = "2",
        Name = "Beth",
        District = "Columbia",
        Level = "10"
    },
    new Person()
    {
        ID = "3",
        Name = "Jim",
        District = "Washington",
        Level = "11"
    }
};  //this already has values
var grpByP = persons
    .GroupBy(p => new { p.District, p.Level })
    .Select(g => new
    {
        g.Key,
        People = g.ToList<Person>()
    });

foreach (var g in grpByP)
{
    Console.WriteLine("Group:");
    Console.WriteLine(g.Key.District);
    Console.WriteLine(g.Key.Level);
    Console.WriteLine("People:");
    foreach (Person p in g.People)
        Console.WriteLine(p.Name);
    Console.WriteLine();
}
Console.ReadLine();

Output:-

Group:
Columbia 10
People:
Joe
Beth

Group:
Washington 11
People:
Jim

LINQ: Converting grouped list into new list

Use SelectMany extension method.

grp is of type IEnumerable<IGrouping<'a, Item>> - so it some kind of list of list.

And you need return flattened list of all items.

List<Item> myDestList = grp.SelectMany(g => g).ToList();

Another approach is using your original list, because your code updating already existed items.

C# LINQ GroupBy to convert a List to a group with one property as List of values

After GroupBy, use ToDictionary:

source.GroupBy(x => x.Name)
      .ToDictionary(x => x.Key, x => x.Select(e => e.Value).ToList());

This yields a Dictionary<string, List<string>> where the keys are the names and the values are lists made up of projecting each element to a string under that specific group.

I assume that Value is a string for example purposes only but in reality, it doesn't really matter as the solution remains the same.

Using Linq to group a list of objects into a new grouped list of list of objects

var groupedCustomerList = userList
    .GroupBy(u => u.GroupID)
    .Select(grp => grp.ToList())
    .ToList();

LINQ groupby to List<List<object>>

I think you are looking this:

var data = Model.Where(x => x.Start.Date == DateTime.UtcNow.Date)
                .GroupBy(x => new { x.Start, x.Field2 })
                .Select(g=>g.ToList()).ToList();

Add a Select call to get a list per each group

Linq: Group List of Dictionary by multiple properties and Form a List

Start with flattening the dictionary values.

var values = _allVertexes.Values.SelectMany(v => v);

Now that you have all the vertexes in one place, it is time to group them up by FeatureClassId and OID.

var grouped = values.GroupBy(v => new { v.FeatureClassId, v.OID });

All that is left now is iterating over the grouped collection and do whatever you want with them.

Alternatively, if you want two level grouping then do grouping on FeatureClassId, then group their elements by OID.

var grouped = values.GroupBy(v => v.FeatureClassId).Select(g => g.GroupBy(v => v.OID));

Group list by multiple conditions, LINQ

With ternary conditional operator

books.GroupBy(b => b.Price < 10 ? 10 : (b.Price < 20 ? 20 : 30));

C# linq group to a list inside a list

Use GroupBy and then Select to define how you want the grouped results projected.

List<UserManagementClass> UsersList = Users
    .GroupBy(u => u.userID)
    .Select(_ => new UserManagementClass
    {
        userID = _.Key,
        UserAgencyList = _.SelectMany(u => u.UserAgencyList.Select(agency => agency)).ToList()
    }).ToList();

Group By Multiple Columns

Use an anonymous type.

Eg

group x by new { x.Column1, x.Column2 }

C# Linq Group By on multiple columns

var consolidatedChildren =
    from c in children
    group c by new
    {
        c.School,
        c.Friend,
        c.FavoriteColor,
    } into gcs
    select new ConsolidatedChild()
    {
        School = gcs.Key.School,
        Friend = gcs.Key.Friend,
        FavoriteColor = gcs.Key.FavoriteColor,
        Children = gcs.ToList(),
    };

---

var consolidatedChildren =
    children
        .GroupBy(c => new
        {
            c.School,
            c.Friend,
            c.FavoriteColor,
        })
        .Select(gcs => new ConsolidatedChild()
        {
            School = gcs.Key.School,
            Friend = gcs.Key.Friend,
            FavoriteColor = gcs.Key.FavoriteColor,
            Children = gcs.ToList(),
        });

---

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