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

public class MainClass {
    public static void Main() {
        string[] presidents = {"Grant", "Harding", "Harrison", "Hayes", "Hoover", "Jackson"};
        Console.WriteLine("presidents count:  " + presidents.Count());
        IEnumerable<string> presidentsWithDupes = presidents.Concat(presidents);
        Console.WriteLine("presidentsWithDupes count:  " + presidentsWithDupes.Count());
        IEnumerable<string> presidentsDistinct = presidentsWithDupes.Distinct();
        Console.WriteLine("presidentsDistinct count:  " + presidentsDistinct.Count());
    }
}

    

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

public class MainClass {
public static void Main() {

List products = GetProductList(); var categoryNames = (
from p in products
select p.Category)
.Distinct();

Console.WriteLine(“Category names:”);
foreach (var n in categoryNames) {
Console.WriteLine(n);
}
}
static List GetProductList() {
List empTree = new List();
empTree.Add(new Product { ProductName = “A”, Category = “O”, UnitPrice = 12, UnitsInStock = 5, Total = 36, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = “B”, Category = “O”, UnitPrice = 2, UnitsInStock = 4, Total = 35, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = “C”, Category = “O”, UnitPrice = 112, UnitsInStock = 3, Total = 34, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = “D”, Category = “O”, UnitPrice = 112, UnitsInStock = 0, Total = 33, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = “E”, Category = “O”, UnitPrice = 1112, UnitsInStock = 2, Total = 32, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = “F”, Category = “O”, UnitPrice = 11112, UnitsInStock = 0, Total = 31, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
return empTree;
}
}
class Product : IComparable {
public string ProductName { get; set; }
public string Category { get; set; }
public int UnitPrice { get; set; }
public int UnitsInStock { get; set; }
public int Total { get; set; }
public DateTime OrderDate { get; set; }
public int Id { get; set; }

public override string ToString() {
return String.Format(“Id: {0}, Name: {1} , Category: {3}”, this.Id, this.ProductName, this.Category);
}
int IComparable.CompareTo(Product other) {
if (other == null)
return 1;
if (this.Id > other.Id)
return 1;

if (this.Id < other.Id) return -1; return 0; } } [/csharp]

   
 

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

public class MainClass {
    public static void Main() {

        int[] fl = { 2, 2, 3, 5, 5 };

        var uniqueFactors = fl.Distinct();

        Console.WriteLine("Prime factors of 300:");
        foreach (var f in uniqueFactors) {
            Console.WriteLine(f);
        }
    }
}

    

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

public class MainClass{
   public static void Main(){
            int[] numbers = {1, 1, 2, 3, 3};
            Console.Write(numbers.Distinct());
   }
}

    

   
 

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

public class MainClass {
    public static void Main() {
        var numbers = new List<int>();
        numbers.Add(1);
        IEnumerable<int> query = numbers.Select(n => n * 10);
        numbers.Add(2);             
        foreach (int n in query)
            Console.Write(n + "|"); 
    }
}

    

   
 

using System;
using System.Collections.Generic;
using System.Linq;
public class MainClass {
    public static void Main() {

        var numbers = new List<int>() { 1, 2 };

        IEnumerable<int> query = numbers.Select(n => n * 10);
        foreach (int n in query) Console.Write(n + "|"); 

        numbers.Clear();
        foreach (int n in query) Console.Write(n + "|"); 

    }
}

    

   
 

using System;
using System.Linq;

class MainClass {
    static double Square(double n) {
        Console.WriteLine("Computing Square(" + n + ")...");
        return Math.Pow(n, 2);
    }

    public static void Main() {
        int[] numbers = { 1, 2, 3 };
        var query = from n in numbers select Square(n);
        foreach (var n in query.ToList())
            Console.WriteLine(n);
    }
}