LINQ - GroupBy a key and then put each grouped item into separate 'buckets'

user_248480 0
Viewed 36747

I have a list of items as such:

public class Item
{
    public int ItemId { get; set; }
    public string ItemName { get; set; }
    public int ListId { get; set; }
}

1 Test1 1

2 Test2 1

3 Test3 1

4 List 2

5 List2 2

6 Testing 3

7 Testing2 3

8 Testing3 3

Is there a way for me to group by the ListId and put them into each separate buckets, i.e, ListId1 bucket will have all items with ListId == 1. The list is dynamically returned from SQL, so I don't know before hand how many ListId there will be.

linq-group linq .net c#
5 Answers
    IList<Student> studentList = new List<Student>()
    { 
    new Student() { StudentID = 1, StudentName = "John", Age = 18 } ,
    new Student() { StudentID = 2, StudentName = "Steve",  Age = 21 } ,
    new Student() { StudentID = 3, StudentName = "Bill",  Age = 18 } ,
    new Student() { StudentID = 4, StudentName = "Ram" , Age = 20 } ,
    new Student() { StudentID = 5, StudentName = "Abram" , Age = 21 } 
    };

var groupedResult = from s in studentList group s by s.Age;

//iterate each group 

foreach (var ageGroup in groupedResult)
{
    Console.WriteLine("Age Group: {0}", ageGroup.Key); //Each group has a key 

    foreach(Student s in ageGroup) // Each group has inner collection
        Console.WriteLine("Student Name: {0}", s.StudentName);
}
user_41236710

Basic format

  var res = (from i in items
                           group i by i.ListId into g
                           select  );
user_61125860

You can also do this by following

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main()
    {
        List<Item> items = new List<Item>();
        items.Add(new Item() { ItemId = 1, ItemName = "Test1", ListId = 1 });
        items.Add(new Item() { ItemId = 2, ItemName = "Test2", ListId = 1 });
        items.Add(new Item() { ItemId = 3, ItemName = "Test3", ListId = 1 });
        items.Add(new Item() { ItemId = 4, ItemName = "List", ListId = 2 });
        items.Add(new Item() { ItemId = 5, ItemName = "List2", ListId = 2 });
        items.Add(new Item() { ItemId = 6, ItemName = "Testing", ListId = 3 });
        items.Add(new Item() { ItemId = 7, ItemName = "Testing2", ListId = 3 });
        items.Add(new Item() { ItemId = 8, ItemName = "Testing3", ListId = 3 });

        var groupByResult = items.GroupBy(i => i.ListId);
        List<GroupedItems> betterGroups = new List<GroupedItems>();
        foreach (var groupedItem in groupByResult)
        {
            betterGroups.Add(new GroupedItems() { ListId = groupedItem.Key, Items = groupedItem.ToList() });
            // ListId = 1 , List<Item> 3 records 
            // ListId = 2 , List<Item> 2 records
            // ListId = 3 , List<Item> 3 records
            // You can iteratre throught ListId
        }
    }
    
    public class Item
    {
        public int ItemId { get; set; }
        public string ItemName { get; set; }
        public int ListId { get; set; }
    }
    
    public class GroupedItems
    {
        public int ListId {get; set;}
        public List<Item> Items {get; set;}
    }
}

donetFiddle example Link

user_18317340
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