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Linq get id of the employee with most entries in table

i am trying to write a linq that will return the id of the employee who has the most entries in the table.
This is how my class looks like
public class TrainingEmployee
{
public int EmployeeId { get; set; }
public int TrainingId { get; set; }
public List<TrainingEmployee> GenerateData()
{
return new List<TrainingEmployee>()
{
new TrainingEmployee() { EmployeeId = 1, TrainingId = 2},
new TrainingEmployee() { EmployeeId = 1, TrainingId = 2},
new TrainingEmployee() { EmployeeId = 1, TrainingId = 2},
new TrainingEmployee() { EmployeeId = 1, TrainingId = 2},
new TrainingEmployee() { EmployeeId = 2, TrainingId = 3},
new TrainingEmployee() { EmployeeId = 2, TrainingId = 3},
new TrainingEmployee() { EmployeeId = 2, TrainingId = 3},
new TrainingEmployee() { EmployeeId = 2, TrainingId = 3},
new TrainingEmployee() { EmployeeId = 2, TrainingId = 5},
new TrainingEmployee() { EmployeeId = 2, TrainingId = 5},
new TrainingEmployee() { EmployeeId = 2, TrainingId = 1},
};
}
}
And this is how my code looks so far
var lista = new TrainingEmployee();
var data = lista.GenerateData().GroupBy(x => x.EmployeeId);
var maxValue = 0;
var employeeId = 0;
foreach (var group in data)
{
var currentlyGroupCount = group.Count();
if(currentlyGroupCount > maxValue)
{
maxValue = currentlyGroupCount;
employeeId = group.Key;
}
}
Console.WriteLine("Value: {0} employeeid: {1}", maxValue, employeeId);
How can i do the above code in just a linq without using that much of a code?

You could order it descending and select the first one:
var employee = GenerateData()
// group on EmployeeId
.GroupBy(e => e.EmployeeId)
// reverse order it on count
.OrderByDescending(g => g.Count())
// select the first
.FirstOrDefault();
// check if the query returned anything other than default.
if(employee != default)
Console.WriteLine("Value: {0} employeeid: {1}", employee.Count(), employee.EmployeeId);

Another approach similar to jeroen-van-langen's answer but using MoreLINQ's MaxBy():
GenerateData()
.GroupBy(e => e.EmployeeId)
.MaxBy(e => e.Count());
This would also return multiple IDs if multiple employee's had the same "max count"; a possibility in your scenario.

This evaluates Count() once for each employees group so is a little more performant, it allows also to get both of employyId and the max count
var mostFrequentEmployeeId = GenerateData()
.GroupBy(x => x.EmployeeId, (employeeId, employeesGroup) => new { employeeId, count = employeesGroup.Count() })
.OrderByDescending(x => x.count)
.FirstOrDefault()?
.employeeId;

ASP.NET-MVC4 - Linq query to select largest "supplier" in a database

i have 2 tables in a database
supplier table: SupplierID - SupplierName
product table: ProductID - ProductName - UnitsInStock - SupplierID
how can i select the supplier that has largest UnitsInStock?
here's the code i have
private storeDBEntities2 db1 = new storeDBEntities2();
public ActionResult Index()
{
var product = db1.Products.Where(e => e.UnitsInStock == 0);
var largestSupplier = db1.Products.GroupBy(e => e.SupplierID);
Product minimord = db1.Products.OrderBy(e => e.UnitsOnOrder).FirstOrDefault();
var supplier = // this is the query i am struggling with
AllModelsProduct all = new AllModelsProduct { Iproduct = product.ToList(), product = new Product(),largestSupplierOfTheStore = supplier,minimumOrders = minimord };
return View(all);
}
here's a picture of my data
i need to get supplierID 345 as we have 20 units belong to him in store which is greater than the other supplier with 5 + 3 + 0 = 8 units

If all you're looking to do is find the supplier with the largest number of UnitsInStock then this should do the trick.
I have created a dotNetFiddle for you to observe.
But here it is anyway:
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
{
List<Supply> lstSuppliers = new List<Supply>();
Supply supply1 = new Supply() { ID = 1, SupplierName = "Supplier One"};
Supply supply2 = new Supply() { ID = 2, SupplierName = "Supplier Two"};
lstSuppliers.Add(supply1);
lstSuppliers.Add(supply2);
Product product1 = new Product() {ID = 1, UnitsInStock = 3, SupplierID = 1};
Product product2 = new Product() {ID = 2, UnitsInStock = 3, SupplierID = 2};
Product product3 = new Product() {ID = 3, UnitsInStock = 5, SupplierID = 1};
List<Product> lstAllProducts = new List<Product>();
lstAllProducts.Add(product1);
lstAllProducts.Add(product2);
lstAllProducts.Add(product3);
var findSupplierId = lstAllProducts.GroupBy(x => x.SupplierID).Select(x => new{ Supplier = x.Key.ToString(), Count = x.Sum(g => g.UnitsInStock)}).OrderByDescending(x => x.Count).First().Supplier;
Console.WriteLine(findSupplierId);
Console.WriteLine(lstSuppliers.Single(x => x.ID.ToString() == findSupplierId).SupplierName);
}
}
public class Supply{
public int ID {get;set;}
public string SupplierName {get;set;}
}
public class Product{
public int ID {get;set;}
public int UnitsInStock {get;set;}
public int SupplierID {get;set;}
}
This uses the GroupBy, along with creating anonymous classes to get the desired outcome.
Let me know if this helps!
Update - To show if multiple suppliers have the same units in stock
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
{
List<Supply> lstSuppliers = new List<Supply>();
Supply supply1 = new Supply() { ID = 1, SupplierName = "Supplier One"};
Supply supply2 = new Supply() { ID = 2, SupplierName = "Supplier Two"};
Supply supply3 = new Supply() { ID = 3, SupplierName = "Supplier Three"};
lstSuppliers.Add(supply1);
lstSuppliers.Add(supply2);
lstSuppliers.Add(supply3);
Product product1 = new Product() {ID = 1, UnitsInStock = 3, SupplierID = 1};
Product product2 = new Product() {ID = 2, UnitsInStock = 3, SupplierID = 2};
Product product3 = new Product() {ID = 3, UnitsInStock = 5, SupplierID = 1};
Product product4 = new Product() {ID = 4, UnitsInStock = 8, SupplierID = 3};
List<Product> lstAllProducts = new List<Product>();
lstAllProducts.Add(product1);
lstAllProducts.Add(product2);
lstAllProducts.Add(product3);
lstAllProducts.Add(product4);
// finds largest supplier
//var findSupplierId = lstAllProducts.GroupBy(x => x.SupplierID).Select(x => new{ Supplier = x.Key.ToString(), Count = x.Sum(g => g.UnitsInStock)}).OrderByDescending(x => x.Count).First().Supplier;
//Console.WriteLine(lstSuppliers.Single(x => x.ID.ToString() == findSupplierId).SupplierName);
// What if there are multiple suppliers with the same number of units in stock?
// first - we have to find the largest number of units in stock
var findLargestNumberUIS = lstAllProducts.GroupBy(x => x.SupplierID).Select(x => new{ Supplier = x.Key.ToString(), Count = x.Sum(g => g.UnitsInStock)}).Max(x => x.Count); // 8
// second - gather a list of suppliers where their units in stock == findLargestNumberUIS
var lstOfLargestSuppliers = lstAllProducts.GroupBy(x => x.SupplierID).Select(x => new{ Supplier = x.Key.ToString(), Count = x.Sum(g => g.UnitsInStock)}).Where(x => x.Count == findLargestNumberUIS).ToList();
// third - loop through lstOfLargestSuppliers to get all suppliers that have the same amount of units in stock which happen to be the largest
foreach(var item in lstOfLargestSuppliers){
var supplier = lstSuppliers.Single(x => x.ID.ToString() == item.Supplier).SupplierName;
Console.WriteLine(supplier); // print the supplier names to console
// Output - Supplier One
// Supplier Three
}
}
}
public class Supply{
public int ID {get;set;}
public string SupplierName {get;set;}
}
public class Product{
public int ID {get;set;}
public int UnitsInStock {get;set;}
public int SupplierID {get;set;}
}

Cannot group data in LINQ

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.

How to set a value in one list when comparing it with other list using LINQ

I have two lists:
List A List B
ID FirstName WorkingID ID FirstName WorkingID
5 John Null 5 John 1
9 Patrick Null 9 Patrick 2
16 Ryan Null 16 Ryan 3
I want to compare these lists using LINQ and if IDs from both lists are equal, I want to set WorkingID in the first list, A list.
Thanks.

Also like this:
A.ForEach(c => c.WorkingID = B.Where(m => m.ID == c.ID).Select(s => s.WorkingID).FirstOrDefault());
Full source:
public class Test
{
public int ID;
public int? WorkingID;
}
class Program
{
static void Main(string[] args)
{
var A = new List<Test>()
{
new Test { ID = 5, WorkingID = null },
new Test { ID = 9, WorkingID = null },
new Test { ID = 16, WorkingID = null },
new Test { ID = 18, WorkingID = null }
};
var B = new List<Test>()
{
new Test { ID = 5, WorkingID = 1 },
new Test { ID = 9, WorkingID = 2 },
new Test { ID = 16, WorkingID = 3 }
};
A.ForEach(c => c.WorkingID = B.Where(m => m.ID == c.ID).Select(s => s.WorkingID).FirstOrDefault());
}
}

Try this:
listA.Where(a => listB.Any(b => a.ID == b.ID))
.ToList()
.ForEach(a => a.WorkingID = listB.First(b => b.ID == a.ID).WorkingID);

You could try something like this (not a pure LINQ approach):
foreach(var item in listA)
{
var itemInB = listB.FirstOrDefault(x=>x.ID==item.ID);
if(itemInB!=null)
item.WorkingID = itemInB.WorkongID
}

var query = from a in lista
join b in listb on a.ID equals b.ID
where b.WorkingID != null
select new {a, b};
foreach (var item in query)
{
item.a.WorkingID = item.b.WorkingID;
}
easy as that.

Here is one way, assuming a class structure as follows:
class MyItem
{
public int ID { get; set; }
public string FirstName { get; set; }
public int WorkingID { get; set; }
}
You can join the second list on matching IDs:
var list1 = new List<MyItem>() {
new MyItem() { ID = 5, FirstName = "John" },
new MyItem() { ID = 9, FirstName = "Patrick" },
new MyItem() { ID = 16, FirstName = "Ryan" },
};
var list2 = new List<MyItem>() {
new MyItem() { ID = 5, FirstName = "John", WorkingID = 1 },
new MyItem() { ID = 9, FirstName = "Patrick", WorkingID = 2 },
new MyItem() { ID = 16, FirstName = "Ryan", WorkingID = 3 },
};
var mergedList = from item1 in list1
join item2 in list2
on item1.ID equals item2.ID
select new MyItem() { ID = item1.ID, FirstName = item1.FirstName, WorkingID = item2.WorkingID };

I think using Join then looping through the list would be more efficient. The below is practically the same as the answer provided by Florian Schmidinger:
A.AsEnumerable().Join(B.AsEnumerable(), a => a.ID, b => b.ID, (a, b) => new { a, b })
.ToList().ForEach(obj => { obj.a.WorkingID = obj.b.WorkingID; });

How to Translate SQL "WHERE expr IN (query)" into LINQ?

Basically I want to make this SQL query with linq:
SELECT *
FROM Orders
WHERE Identifier IN (SELECT DISTINCT [Order] FROM OrderRows WHERE Quantity = '1')
This is what I have come up with:
var q = from o in db.Orders
where o.Identifier in (from r in db.OrderRows
where r.Quantity == 1 select r.Order).Distinct());
But the in after o.Identifier is not valid.
What is the correct syntax for the keyword IN?

I'm a little late, but I made a demo!
As other people have stated, I always use Contains:
using System;
using System.Collections.Generic;
using System.Linq;
namespace ContainsExample
{
class Program
{
static void Main(string[] args)
{
var foos = new List<Foo>
{
new Foo { ID = 1, FooName = "Light Side" },
new Foo { ID = 2, FooName = "Dark Side" }
};
var bars = new List<Bar>
{
new Bar { ID = 1, BarName = "Luke", FooID = 1 },
new Bar { ID = 2, BarName = "Han", FooID = 1 },
new Bar { ID = 3, BarName = "Obi-Wan", FooID = 1 },
new Bar { ID = 4, BarName = "Vader", FooID = 2 },
new Bar { ID = 5, BarName = "Palpatine", FooID = 2 },
new Bar { ID = 6, BarName = "Fett", FooID = 2 },
new Bar { ID = 7, BarName = "JarJar", FooID = 3 }
};
var criteria = from f in foos
select f.ID;
var query = from b in bars
where criteria.Contains(b.FooID)
select b;
foreach (Bar b in query)
{
Console.WriteLine(b.BarName);
}
Console.WriteLine();
Console.WriteLine("There should be no JarJar...");
Console.ReadLine();
}
}
public class Foo
{
public int ID { get; set; }
public string FooName { get; set; }
}
public class Bar
{
public int ID { get; set; }
public string BarName { get; set; }
public int FooID { get; set; }
}
}

from o in db.Orders
where o.Identifier.Any
(
from r in db.OrderRows
where r.Quantity == 1
select r.Order
).Distinct()
select o
Try this...

It seems like you want a join:
var q = (from o in db.Orders
join r in db.OrderRows on o.Identifier equals r.Order
where r.Quantity == 1
select o).Distinct();

var q = from o in db.Orders
where (from r in db.OrderRows
where r.Quantity == 1 select r.Order).Distinct().Contains(o.Identifier);

The short answer is you want to take advantage of the Contains method.
int[] ids = { 2, 5, 6, 1 };
var a = from myRecords in context.db
where ids.Contains (myRecords.id)
select new {Id = myRecords.id};
Filtering on two sets of results works the same way, in that you can filter on any common property shared by the two sets:
string[] cities = { "London", "Paris", "Seattle" };
var query = dataContext.Customers.Where (c => cities.Contains (c.City));

have you tried using something like this:
int[] inKeyword = { 5, 7, 9 };
var q = from o in db.Orders.Where(p => inKeyword.Contains(p.Identifier));
Hope it helps :)