Csharp/C Sharp/LINQ/Union

prints the unique elements of two integer arrays

 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
    public static void Main() {
        int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
        int[] numbersB = { 1, 3, 5, 7, 8 };
        var uniqueNumbers = numbersA.Union(numbersB);
        Console.WriteLine("Unique numbers from both arrays:");
        foreach (var n in uniqueNumbers) {
            Console.WriteLine(n);
        }
    }
}

prints unique letters from Product and Customer names

 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
    public static void Main() {
        List<Product> products = GetProductList();
        List<Customer> customers = GetCustomerList();
        var productFirstChars =
            from p in products
            select p.ProductName[0];
        var customerFirstChars =
            from c in customers
            select c.rupanyName[0];
        var uniqueFirstChars = productFirstChars.Union(customerFirstChars);
        Console.WriteLine("Unique first letters from Product names and Customer names:");
        foreach (var ch in uniqueFirstChars) {
            Console.WriteLine(ch);
        }
    }
    static List<Product> GetProductList() {
        List<Product> empTree = new List<Product>();
        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;
    }
    static List<Customer> GetCustomerList() {
        List<Product> empTree = new List<Product>();
        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 });
        List<Customer> l = new List<Customer>();
        l.Add(new Customer { CompanyName = "A", Region = "R1", UnitsInStock = 1, Orders = empTree, CustomerId = 0 });
        l.Add(new Customer { CompanyName = "B", Region = "R2", UnitsInStock = 2, Orders = empTree, CustomerId = 1 });
        l.Add(new Customer { CompanyName = "C", Region = "R3", UnitsInStock = 3, Orders = empTree, CustomerId = 2 });
        l.Add(new Customer { CompanyName = "D", Region = "R4", UnitsInStock = 4, Orders = empTree, CustomerId = 3 });
        l.Add(new Customer { CompanyName = "E", Region = "R5", UnitsInStock = 5, Orders = empTree, CustomerId = 4 });
        return l;
    }
}
class Customer : IComparable<Customer> {
    public string CompanyName { get; set; }
    public string Region { get; set; }
    public List<Product> Orders { get; set; }
    public int UnitsInStock { get; set; }
    public int CustomerId { get; set; }
    public override string ToString() {
        return String.Format("Id: {0}, Name: {1}, Region: {3}", this.CustomerId, this.rupanyName, this.Region);
    }
    int IComparable<Customer>.rupareTo(Customer other) {
        if (other == null)
            return 1;
        if (this.CustomerId > other.CustomerId)
            return 1;
        if (this.CustomerId < other.CustomerId)
            return -1;
        return 0;
    }
}
class Product : IComparable<Product> {
    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<Product>.rupareTo(Product other) {
        if (other == null)
            return 1;
        if (this.Id > other.Id)
            return 1;
        if (this.Id < other.Id)
            return -1;
        return 0;
    }
}

Union does appends one sequence to another with duplicates removed:

 
using System;
using System.Collections.Generic;
using System.Linq;
public class MainClass {
    public static void Main() {
        int[] seq1 = { 1, 2, 3 };
        int[] seq2 = { 3, 4, 5 };
        IEnumerable<int> concat = seq1.Concat(seq2);    //  { 1, 2, 3, 3, 4, 5 }
        IEnumerable<int> union = seq1.Union(seq2);     //  { 1, 2, 3, 4, 5 }
    }
}

Union Operator

 
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {
        string[] presidents = {"ant", "arding", "arrison", "eyes", "over", "ackson"};
        IEnumerable<string> first = presidents.Take(5);
        IEnumerable<string> second = presidents.Skip(4);
        IEnumerable<string> concat = first.Concat<string>(second);
        IEnumerable<string> union = first.Union<string>(second);
        Console.WriteLine("The count of the array is: " + presidents.Count());
        Console.WriteLine("The count of the first sequence is: " + first.Count());
        Console.WriteLine("The count of the second sequence is: " + second.Count());
        Console.WriteLine("The count of the concat sequence is: " + concat.Count());
        Console.WriteLine("The count of the union sequence is: " + union.Count());
    }
}

Use Linq to union two arrays

 
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, 3, 3};
            int[] numbers2 = {1, 2, 3, 4};
            Console.Write(numbers.Union(numbers2));
   }
}