LINQ

Use First to return the first matching element as a Product

Posted on by coder

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

public class MainClass {
public static void Main() {

List products = GetProductList();
Product product12 = (
from p in products
where p.Id == 2
select p)
.First();

Console.Write(product12.Category);
}
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 = 2 });
empTree.Add(new Product { ProductName = “C”, Category = “O”, UnitPrice = 112, UnitsInStock = 3, Total = 34, OrderDate = new DateTime(2005, 1, 1), Id = 3 });
empTree.Add(new Product { ProductName = “D”, Category = “O”, UnitPrice = 112, UnitsInStock = 0, Total = 33, OrderDate = new DateTime(2005, 1, 1), Id = 4 });
empTree.Add(new Product { ProductName = “E”, Category = “O”, UnitPrice = 1112, UnitsInStock = 2, Total = 32, OrderDate = new DateTime(2005, 1, 1), Id = 5 });
empTree.Add(new Product { ProductName = “F”, Category = “O”, UnitPrice = 11112, UnitsInStock = 0, Total = 31, OrderDate = new DateTime(2005, 1, 1), Id = 6 });
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]

First with string method

Posted on by coder 
   
 

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

public class MainClass {
    public static void Main() {
        string[] presidents = {"G", "H", "a", "H", "over", "Jack"};

        string name = presidents.First(p => p.StartsWith("H"));
        Console.WriteLine(name);
    }
}

Use First, Last with expression

Posted on by coder 
   
 
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, 2, 3, 4, 5, 6, 7, 8, 9 };
       var query = numbers.First();
       Console.WriteLine("The first element in the sequence");
       Console.Write(query);
       query = numbers.Last();
       Console.WriteLine("The last element in the sequence");
       Console.Write(query);
       Console.WriteLine("The first even element in the sequence");
       query = numbers.First(n => n % 2 == 0);
       Console.Write(query);
       Console.WriteLine("The last even element in the sequence");
       query = numbers.Last(n => n % 2 == 0);
       Console.Write(query);
   }
}

Calling the Filter Method with a Lambda Expression

Posted on by coder 
   
 
using System;
using System.Collections;

public delegate bool IntFilter(int i);

public class MainClass {
    public static int[] FilterArrayOfInts(int[] ints, IntFilter filter) {
        ArrayList aList = new ArrayList();
        foreach (int i in ints) {
            if (filter(i)) {
                aList.Add(i);
            }
        }
        return ((int[])aList.ToArray(typeof(int)));
    }
    public static void Main() {
        int[] nums = { 1, 2, 3, 4, 5};
        int[] oddNums = FilterArrayOfInts(nums, i => ((i &amp; 1) == 1));
        foreach (int i in oddNums)
            Console.WriteLine(i);
    }
}

Calling the Filter Method with an Anonymous Method

Posted on by coder 
   
 
using System;
using System.Collections;

public delegate bool IntFilter(int i);

public class MainClass {
    public static int[] FilterArrayOfInts(int[] ints, IntFilter filter) {
        ArrayList aList = new ArrayList();
        foreach (int i in ints) {
            if (filter(i)) {
                aList.Add(i);
            }
        }
        return ((int[])aList.ToArray(typeof(int)));
    }
    public static void Main() {

        int[] nums = { 1, 2, 3, 4, 5, 6};

        int[] oddNums = FilterArrayOfInts(nums, delegate(int i) { return ((i &amp; 1) == 1); });

        foreach (int i in oddNums)
            Console.WriteLine(i);
    }
}

Calling the Common Library Filter Method

Posted on by coder 
   
 

using System.Collections;
using System;

public delegate bool IntFilter(int i);

public class MainClass {
    public static void Main() {
        int[] nums = { 1, 2, 3, 4, 5, 6};
        int[] oddNums = FilterArrayOfInts(nums, IsOdd);
        foreach (int i in oddNums)
            Console.WriteLine(i);
    }
    public static bool IsOdd(int i) {
        return ((i &amp; 1) == 1);
    }
    public static int[] FilterArrayOfInts(int[] ints, IntFilter filter) {
        ArrayList aList = new ArrayList();
        foreach (int i in ints) {
            if (filter(i)) {
                aList.Add(i);
            }
        }
        return ((int[])aList.ToArray(typeof(int)));
    }
}