I have a list in this table
public class Fruits
{
public int ID { get; set; }
public string Name{ get; set; }
}
I want to know what are the most frequent fruit in this table what is the code that appears to me this result
I am use
var max = db.Fruits.Max();
There is an error in that?
Try
public class Fruits
{
public int ID { get; set; }
public string Name{ get; set; }
}
var Val = fruitList.GroupBy(x => x.ID,
(key, y) => y.MaxBy(x => x.ID).value)
As Drew said in the comments, you want to GroupBy on the value that you care about (I did Name, since ID tends to be unique in most data structures) and then OrderByDescending based on the count.
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
{
var fruits = new List<Fruit> { new Fruit { ID = 1, Name = "Apple" }, new Fruit { ID = 2, Name = "Apple" }, new Fruit { ID = 3, Name = "Pear" } };
var most = fruits.GroupBy(f => f.Name).OrderByDescending(group => group.Count());
Console.WriteLine(most.First().Key);
}
}
public class Fruit
{
public int ID { get; set; }
public string Name{ get; set; }
}
If you want to get the name of the item that exists most in your list, first find the id that is most occurring:
var fruitAnon = fruits
.GroupBy(item => item.ID)
.Select(item => new {
Key = item.Key,
Count = item.Count()
})
.OrderByDescending(item => item.Count)
.FirstOrDefault();
This will return an anonymous object that will have the most frequent id, and the count represents the number of times it exists in the list. You can then find that object's name:
var fruit = fruits.FirstOrDefault(x => x.ID == fruitAnon.Key);
If you had a list like this:
List<Fruits> fruits = new List<Fruits>() {
new Fruits { ID = 1, Name = "Apple" },
new Fruits { ID = 1, Name = "Apple" },
new Fruits { ID = 2, Name = "Orange" },
new Fruits { ID = 2, Name = "Orange" },
new Fruits { ID = 2, Name = "Orange" },
new Fruits { ID = 2, Name = "Orange" }
};
Then:
Console.WriteLine(fruit.Name);
Would print Orange.
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; }
}
Below is my List collection.
public class A
{
public String id{ get; set; }
public string name{ get; set; }
public List<B> nestedList { get; set; }
}
public class B
{
public String innerid{ get; set; }
public string innername { get; set; }
}
I want to use group by on nested collection properties
So I can have output as
innerid="1",
innername="Name1",
{
id= "1", name= "One"
id= "2", name= "Two"
id= "4", name= "Four"
}
innerid="2",
innername="Name2",
{
id= "3", name= "Three"
id= "6", name= "Six"
id= "8", name= "Eight"
}
I tried
.GroupBy(a => a.nestedList.First().innerid).ToList()
But I am not getting required output.
You want to reverse the hierarchy, so grouping by the nested-B and list the parent-A as children?
var groups = aList
.SelectMany(a => a.nestedList.Select(b => new { A = a, B = b }))
.GroupBy(x => new { x.B.innerid, x.B.innername })
.Select(g => new {
g.Key.innerid,
g.Key.innername,
aItems = g.Select(x => new { x.A.id, x.A.name })
});
Instead of selecting anonymous types you can also select the original A and B instances.
Assuming the items from the result must contain items of type A, you could use query syntax to solve this:
var grouping = from a in collectionOfA
from b in a.nestedList
group a by new { b.innerid, b.innername } into g
select new
{
innerid = g.Key.innerid,
innername = g.Key.innername,
items = g.ToList()
};
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 an Array of colors viz.
var colorPallete = new string[]{color1, color2, color3, color4, color5};
I also have a list of objects which contains an ID.
eg. var previousList<MyModel> = new List<MyModel>();
MyModel.cs
public class MyModel()
{
public int ID {get; set;}
public string Class{get; set;}
public string Name {get; set;}
public string Color {get; set;}
}
I want to assign the objects with same ID with a certain color. And then add the assigned color as a new value to the list.
for eg:
Previous list :-
ID :1
Name: abc
Class: Senior
ID :2
Name: xyz
Class: Medium
ID :3
Name: pqr
Class: junior
ID :1
Name: mno
Class: junior
New List :-
ID :1
Name: abc
Class: Senior
Color :color1
ID :2
Name: xyz
Class: Medium
Color :color2
ID :3
Name: pqr
Class: junior
Color :color3
ID :1
Name: mno
Class: junior
Color :color1
This works for me:
var colorPallete = new string[]
{
"color1", "color2", "color3", "color4", "color5",
};
var previousList = new []
{
new { ID = 1, Name = "abc", Class = "Senior", },
new { ID = 2, Name = "xyz", Class = "Medium", },
new { ID = 3, Name = "pqr", Class = "junior", },
new { ID = 1, Name = "mno", Class = "junior", },
};
var newList =
previousList
.Select(x => new
{
x.ID,
x.Name,
x.Class,
Color = colorPallete.ElementAtOrDefault(x.ID - 1),
})
.ToList();
I get this result:
With the question update providing the class MyModel the code can then be written like so:
var colorPallete = new string[]
{
"color1", "color2", "color3", "color4", "color5",
};
var previousList = new List<MyModel>()
{
new MyModel() { ID = 1, Name = "abc", Class = "Senior", },
new MyModel() { ID = 2, Name = "xyz", Class = "Medium", },
new MyModel() { ID = 3, Name = "pqr", Class = "junior", },
new MyModel() { ID = 1, Name = "mno", Class = "junior", },
};
var newList =
previousList
.Select(x => new MyModel()
{
ID = x.ID,
Name = x.Name,
Class = x.Class,
Color = colorPallete.ElementAtOrDefault(x.ID - 1),
})
.ToList();
Which gives:
Now, this approach produces a new list keeping the old list and the old objects intact. Generally this is what you should try to do. It's best to mutate objects only when you know that's what they're designed to do.
So it becomes possible to do an in-place update of the original list like so:
previousList.ForEach(x => x.Color = colorPallete.ElementAtOrDefault(x.ID - 1));
This results in modifying the previousList objects without creating a newList.
If you are using List<T> (not IEnumerable<T>) and you don't want to create a new list, but need to update values in the existing list instead, you can do it with the single query. There are three ways to process your scenario (A, B, C):
var colorPallete = new string[]
{
"Red", "Green", "Blue"
};
var list = new List<MyModel>()
{
new MyModel() { ID = 1, Name = "model1", Class = "A", },
new MyModel() { ID = 1, Name = "model11", Class = "AA", },
new MyModel() { ID = 2, Name = "model2", Class = "B", },
new MyModel() { ID = 3, Name = "model3", Class = "C", },
new MyModel() { ID = 4, Name = "model4", Class = "D", },
new MyModel() { ID = 5, Name = "model5", Class = "E", },
};
//A. This code assigns null for unknown IDs
//I.e. if (ID > 0 && ID < colorPallete.Length) then color will be picked from colorPallete[],
//else it will be null
list.ForEach(x => x.Color = colorPallete.ElementAtOrDefault(x.ID - 1));
//B. This code apply some default color for unknown IDs
//I.e. if (ID > 0 && ID < colorPallete.Length) then color will be picked from colorPallete,
//else it will be "DefaultColor"
list.ForEach(x => x.Color = colorPallete.ElementAtOrDefault(x.ID - 1) ?? "DefaultColor");
//C. This code can assign the same color to models with different IDs,
//but models with identical IDs always will have identical color
list.ForEach(x => x.Color = colorPallete.ElementAtOrDefault((x.ID - 1) % colorPallete.Length));
I would create a class for the objects with a color property like this:
public class MyClass
{
public int ID { get; set; }
public string Name { get; set; }
public string Class { get; set; }
public string Color { get; set; } // Nullable
}
And for the colors I would create another class with an ID to compare with the ID of MyClass:
public class MyColor
{
public int ID { get; set; }
public string Color { get; set; }
}
For each color in colorPalette you would assign an ID that matches the ID of the list of MyClass.
So at first the color from MyClass would be null. And then you could loop over the list of MyClass:
foreach (MyClass myClass in myClassList)
{
myClass.Color = colorPalette.FirstOrDefault(col => col.ID = myClass.ID);
}
Or without an ID in Color class (comparing the names of the variables which is not a beautiful solution):
foreach (MyClass myClass in myClassList)
{
myClass.Color = colorPalette.FirstOrDefault(col => int.Parse(nameof(col.Color).Replace("color", "")) == myClass.ID);
}
I have classes
public class DevicePart
{
public int Id {get;set;}
public string Name {get;set;}
public int Distance {get;set;}
}
public class Device
{
public int ID {get;set;}
public string Name {get;set;}
public List<DevicePart> Parts {get;set;}
}
public class Data
{
public int Id{get;set;}
public string Name{get;set;}
public int ParentId{get;set;}
public int Distance{get;set;}
}
and I have list with Data:
1;Phone;0;0
2;TV;0;0
3;battery;1;5
4;button;1;3
5;webcam;2;5
how can I create optimal and faster linq query(or recursion procedure) to create object List<Device> from my Data list
Try this:
var data = new List<Data>()
{
new Data() { Id = 1, Name = "Phone", ParentId = 0, Distance = 0 },
new Data() { Id = 2, Name = "TV", ParentId = 0, Distance = 0 },
new Data() { Id = 3, Name = "battery", ParentId = 1, Distance = 5 },
new Data() { Id = 4, Name = "button", ParentId = 1, Distance = 3 },
new Data() { Id = 5, Name = "webcam", ParentId = 2, Distance = 5 },
};
var lookup = data.ToLookup(x => x.ParentId);
var devices =
lookup[0]
.Select(x => new
{
ID = x.Id,
x.Name,
Parts =
lookup[x.Id]
.Select(y => new
{
y.Id,
y.Name,
y.Distance,
})
.ToList(),
})
.ToList();
It gives me this: