I have list that includes class named 'ID', 'Name' and 'Category'. There are 6 item in list.
List<MyData> list =
{
{0, "John", "Police"},
{1,"Michael", "Police"},
{2,"Alice", "Police"},
{3, "Ferdinand", "Thief"},
{4, "Jocas", "Thief"},
{5, "Connor", "Thief"}
};
I wanna list them with limited quantity per group by 'Category' with LINQ.
Example : I want list 2 item for each 'Cateogory'. Listed should be below :
John Police
Michael Police
Ferdinand Thief
Jocas Thief
Use combination of Take and SelectMany:
var results = list.GroupBy(x => x.Category).SelectMany(g => g.Take(2)).ToList();
I've tested it on following Item class:
public class Item
{
public int ID { get; set; }
public string Name { get; set; }
public string Category { get; set; }
}
And query:
List<Item> list = new List<Item>
{
new Item { ID = 0, Name = "John", Category = "Police"},
new Item { ID = 1, Name = "Michael", Category = "Police"},
new Item { ID = 2, Name = "Alice", Category = "Police"},
new Item { ID = 3, Name = "Ferdinand", Category = "Thief"},
new Item { ID = 4, Name = "Jocas", Category = "Thief"},
new Item { ID = 5, Name = "Connor", Category = "Thief"}
};
var results = list.GroupBy(x => x.Category).SelectMany(g => g.Take(2)).ToList();
Returns 4 elements, right as you want.
Related
I have list say list of customers and inside each list there is another list of orders
Class Customer
{
int ID,
string Name
List<Order> orders
}
Class Order{
int ID,
string Name
}
Also have a integer list of filteredorderIds = {1,2,3,4}
I want to filter the list of customers who has got orderIds from filteredorderIds list.
So far I am stuck at query like
var filteredCustomers = Customers.Where(x => x.Orders.Any(filteredorderIds.contains(y => y.Id)));
please give credit to #Johnathan Barclay, since he posted faster than i typed example
void Main()
{
var customers = new List<Customer>(){
new Customer(){
ID =1,
Name = "Cust1",
orders = new List<Order>(){
new Order(){ID = 4, Name = "o11"},
new Order(){ID = 5, Name = "o12"},
new Order(){ID = 6, Name = "o13"}
}
},
new Customer(){
ID = 2,
Name = "Cust2",
orders = new List<Order>(){
new Order(){ID = 3, Name = "o21"},
new Order(){ID = 7, Name = "o22"},
new Order(){ID = 8, Name = "o23"}
}
}
};
customers.Where(w =>
w.orders.Any(w => filteredorderIds.Contains(w.ID))
).Dump();
}
List<int> filteredorderIds = new List<int>() { 1, 2, 3, 4 };
public class Customer
{
public int ID { get; set; }
public string Name { get; set; }
public List<Order> orders { get; set; }
}
public class Order
{
public int ID { get; set; }
public string Name { get; set; }
}
I have a object list like this:
using System;
using System.Collections.Generic;
using System.Linq;
public class Item
{
public int Id;
public int Price;
}
public class Program
{
public static void Main()
{
List<Item> food = new List<Item> {
new Item { Id = 1, Price = 1},
new Item { Id = 2, Price = 3},
new Item { Id = 4, Price = 9}
};
List<Item> drinks = new List<Item> {
new Item { Id = 1, Price = 1},
new Item { Id = 2, Price = 2},
new Item { Id = 3, Price = 0},
new Item { Id = 4, Price = 1},
new Item { Id = 6, Price = 1}
};
List<Item> magazines = new List<Item> {
new Item { Id = 3, Price = 1},
new Item { Id = 5, Price = 2},
};
var combined = food.Union(drinks).Union(magazines).Distinct().ToList();
}
}
What I want to do is, add all the prices into one list. Without any duplicates (Id). My goal is to have the total sum of the prices. So basically add all prices for the same ID together.
So the combined list should look like this:
List<Item> combined = new List<Item> {
new Item { Id = 1, Price = 2},
new Item { Id = 2, Price = 5},
new Item { Id = 3, Price = 1},
new Item { Id = 4, Price = 10},
new Item { Id = 5, Price = 2},
new Item { Id = 6, Price = 1}
};
Preferably using LINQ.
If you need to get a sum of prices for concatenated List<Item>, you should use GroupBy method to group the items by Id and then Sum of prices for every group
var combined = food.Concat(drinks).Concat(magazines)
.GroupBy(i => i.Id, i => i.Price, (i, prices) => new Item { Id = i, Price = prices.Sum() })
.OrderBy(i => i.Id).ToList();
You can also add OrderBy to sort the results by Id property, if it's important
var x =
// First, combine all lists
food.Concat(drinks).Concat(magazines)
// Group combined Items by Id
.GroupBy(item => item.Id)
// From all groups create final Items with Id and summed Price
.Select(g => new Item { Id = g.Key, Price = g.Sum(item => item.Price) });
I would like to be able to attain the same results that I can get by using foreach on a grouping when using the select method and an anonymous method.
public class ExportData
{
public int Id { get; set; }
public string Colour { get; set; }
public string Name { get; set; }
public int Age { get; set; }
public int Money { get; set; }
}
public class ExportDataDictionary
{
public IDictionary<string, object> ColumnData { get; set; } = new Dictionary<string, object>();
}
Given the two classes above as an example.
I create some data..
var dataCollection = new List<ExportData>
{
new ExportData { Name = "Name1", Age = 1, Colour = "Blue", Id = 1, Money = 10 },
new ExportData { Name = "Name1", Age = 2, Colour = "Red", Id = 2, Money = 20 },
new ExportData { Name = "Name1", Age = 2, Colour = "Green", Id = 3, Money = 30 },
new ExportData { Name = "Name2", Age = 1, Colour = "Yellow", Id = 4, Money = 40 },
new ExportData { Name = "Name3", Age = 2, Colour = "Blue", Id = 5, Money = 50 },
new ExportData { Name = "Name4", Age = 3, Colour = "Blue", Id = 6, Money = 10 }
};
Next I group this data by, for example, two properties as follows..
var dataGrouping = dataCollection.GroupBy(g => new { g.Name, g.Age });
I then create a list of ExportDataDictionaries and foreach through each group in the grouping, creating a new ExportDataDictionary each time and adding both of the keys to the dictionary.
var data = new List<ExportDataDictionary>();
foreach (var grouping in dataGrouping)
{
var datadictionary = new ExportDataDictionary();
datadictionary.ColumnData.Add("NAME", grouping.Key.Name);
datadictionary.ColumnData.Add("AGE", grouping.Key.Age);
data.Add(datadictionary);
}
The result is a collection of 5 ExportDataDictionaries with 2 Columns in each one that contain the pair of keys that correspond to each of the groupings.
My attempt to achieve the same with the Select method is shown below.
var data2 = new List<ExportDataDictionary>();
var mydata = dataGrouping.Select(d =>
{
var datadictionary = new ExportDataDictionary();
datadictionary.ColumnData.Add("NAME", d.Key.Name);
datadictionary.ColumnData.Add("AGE", d.Key.Age);
data2.Add(datadictionary);
return data2;
});
The result is of the type:
mydata = {System.Linq.Enumerable.WhereSelectEnumerableIterator<System.Linq.IGrouping<<>f__AnonymousType0<string, int>, ConsoleApp2.Program.ExportData>, System.Collections.Generic.List<ConsoleApp2.Program.ExportDataDictionary>>}
and it contains 5 items and each item contains 10 dictionaries. The 5 dictionaries that I expect are there with the same values as when using foreach but then there are 2 copies of each. I believe that this must be because it is creating the dictionaries for both of the keys used in the grouping. So, I am wondering how to only do this for one of the keys or just each group in the collection?
The requirement is that mydata should contain the same result as obtained by foreach in data variable
Any help much appreciated :)
Just Add .ToList() at the end of your last statement remove the data2.Add(datadictionary); statement and only return the datadictionary return datadictionary; like this
var mydata = dataGrouping.Select(d =>
{
var datadictionary = new ExportDataDictionary();
datadictionary.ColumnData.Add("NAME", d.Key.Name);
datadictionary.ColumnData.Add("AGE", d.Key.Age);
return datadictionary;
}).ToList();
I have run your code and checked and saw that mydata contains 5 items, and each item contains 2 ColumnData members.
Actually, your Linq query is only executed when you call the .ToList() function
I have a question about a LINQ grouping.
I thought that grouping would be a simple matter of using the GroupBy function on the result set and specifying what to group it by. However my items appear to not be grouping together and instead are displaying as if the GroupBy function wasn't there. I want to group by the itemPk, but I'm can't seem to do it. I have tried grouping by both category.ItemFk and Item.Itempk, but no luck. Could someone give me a pointer on this?
var itemIds = items.Select(i => i.ItemId).ToList();
var itemAndCatJoin =
from item in Context.SCS_Items
join category in Context.SCS_ItemCategories
on item.ItemPk equals category.ItemFk
into temp
from category in temp.DefaultIfEmpty()
select new ExportItemTable
{
Category = category,
Item = item
};
return itemAndCatJoin.Where(i => itemIds.Contains(i.Item.ItemPk))
.GroupBy(n => new {n.Item, n.Category})
.Select(i => new ExportableItem
{
ItemPk = i.Key.Item.ItemPk,
Name = i.Key.Item.Name,
Description = i.Key.Item.Description,
Price = i.Key.Item.Price,
Category = i.Key.Category.Category.Category_Name,
GLDepartment = i.Key.Category.GL_Department.Name ?? "",
GLName = i.Key.Category.GL_Name.Name ?? "",
StartDate = i.Key.Item.StartDate,
EndDate = i.Key.Item.EndDate,
FiscalYear = i.Key.Item.SCS_FiscalYear.Name,
School = i.Key.Item.School != null ? i.Key.Item.School.School_Name : i.Key.Item.Board.Board_Name,
Beneficiary = i.Key.Item.SCS_Beneficiary.Name,
Quantity = i.Key.Item.MaxQuantity,
Deleted = i.Key.Item.DeletedFlag,
OptionalStudents = i.Key.Item.SCS_Attachments.Where(a => !a.IsRequired).SelectMany(a => a.SCS_StudentAttachments).Where(s => !s.DeletedFlag).Select(s => s.StudentFk).Distinct().Count(),
RequiredStudents = i.Key.Item.SCS_Attachments.Where(a => a.IsRequired).SelectMany(a => a.SCS_StudentAttachments).Where(s => !s.DeletedFlag).Select(s => s.StudentFk).Distinct().Count(),
IsPublic = i.Key.Item.IsPublic,
AllowRecurring = i.Key.Item.AllowRecurringPayments,
EffectiveCutoff = i.Key.Item.SCS_Attachments.Where(a => !a.DeletedFlag && a.CourseDropCutoff.HasValue).Select(a => a.CourseDropCutoff).OrderBy(a => a).FirstOrDefault(),
CreatedDate = i.Key.Item.CreatedDate
}).OrderBy(i => i.ItemPk).ToList();
}
your groupbyy is indeed doing nothing for you, you need to tell the groupby what to group by....
like
.GroupBy(n => n.Category)
Here is a simple example to your grouping question:
class Program
{
static void Main()
{
var allItems = GetAllItems();
var groups = from item in allItems
group item by item.Category
into newGroup
select newGroup;
foreach (var group in groups)
{
Console.WriteLine($"\nCategory: {group.Key}");
foreach (var item in group)
{
Console.WriteLine($"{item.Name}: {item.Price}");
}
}
Console.ReadLine();
}
static List<Category> GetAllCategories()
{
return new List<Category>()
{
new Category() { Id = 1, Name = "Programming Books" },
new Category() { Id = 2, Name = "Fiction Books" }
};
}
static List<Item> GetAllItems()
{
return new List<Item>()
{
new Item() { Id = 1, Name = "Embedded Linux", Category = 1, Price = 9.9 },
new Item() { Id = 2, Name = "LINQ In Action", Category = 1, Price = 36.19 },
new Item() { Id = 3, Name = "C# 6.0 and the .NET 4.6 Framework", Category = 1, Price = 40.99 },
new Item() { Id = 4, Name = "Thinking in LINQ", Category = 1, Price = 36.99 },
new Item() { Id = 5, Name = "The Book Thief", Category = 2, Price = 7.99 },
new Item() { Id = 6, Name = "All the Light We Cannot See", Category = 2, Price = 16.99 },
new Item() { Id = 7, Name = "The Life We Bury", Category = 2, Price = 8.96 }
};
}
}
public class Item
{
public int Id { get; set; }
public string Name { get; set; }
public double Price { get; set; }
public int Category { get; set; }
}
public class Category
{
public int Id { get; set; }
public string Name { get; set; }
}
This example is simple enough for anyone new to LINQ. I am sure you can make some adjustment to make it work for your specific issue. Hope this will help.
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.
You can use GroupBy:
var groups = items.GroupBy(item => item.ListId);
foreach(var group in groups)
{
Console.WriteLine("List with ID == {0}", group.Key);
foreach(var item in group)
Console.WriteLine(" Item: {0}", item.ItemName);
}
Let's create your list of items:
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);
After this GroupBy call, groupByResult is a variable of type IEnumerable<IGrouping<int, Item>> which is basically a collection of objects that implement IGrouping interface. This allows you to iterate through all items as IGrouping is derived from IEnumerable<> and has an extra field named Key:
public interface IGrouping<out TKey, out TElement> : IEnumerable<TElement>, IEnumerable
{
TKey Key { get; }
}
Briefly said, a GroupBy method call returns a list of lists. An outer list corresponds to 'buckets' as you mentioned in your question. Then each 'bucket' contains items corresponding to that 'bucket'. To be specific to your example, the value of groupByResult is depicted in this screenshot. As we can see there, your initial collection was grouped into three different buckets that have 3, 2 and 3 items, respectively.
As for accessing items in these groups, you can use simple LINQ:
List<Item> firstBucketItems = groupByResult.First(i => i.Key == 1).ToList();
List<Item> secondBucketItems = groupByResult.First(i => i.Key == 2).ToList();
List<Item> thirdBucketItems = groupByResult.First(i => i.Key == 3).ToList();
Or you can just iterate through all items:
foreach (var itemGroup in groupByResult)
{
int groupKey = itemGroup.Key;
foreach (Item item in itemGroup)
{
// Do whatever...
}
}
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);
}
Basic format
var res = (from i in items
group i by i.ListId into g
select );
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