Csharp/CSharp Tutorial/LINQ/Contains

A query to extract strings containing the letter "a", sorted by length and converted to uppercase

using System;
using System.Collections.Generic;
using System.Linq;
class LinqDemo {
    static void Main() {
        string[] names = { "J", "P", "G", "Pa" };
        IEnumerable<string> query =
          from n in names
          where n.Contains("a")     
          orderby n.Length          
          select n.ToUpper();       
        foreach (string name in query) Console.Write(name + "/");
    }
}

Contains with IEqualityComparer

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MyStringifiedNumberComparer : IEqualityComparer<string> {
    public bool Equals(string x, string y) {
        return (Int32.Parse(x) == Int32.Parse(y));
    }
    public int GetHashCode(string obj) {
        return Int32.Parse(obj).ToString().GetHashCode();
    }
}
public class MainClass {
    public static void Main() {
        string[] stringifiedNums = {"001", "49", "017", "0080", "00027", "2" };
        bool contains = stringifiedNums.Contains("2",new MyStringifiedNumberComparer());
        Console.WriteLine(contains);
    }
}

Contains with predicate returned false

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {
        string[] presidents = {"A", "H", "a", "H", "over", "Jack"};
        bool contains = presidents.Contains("G");
        Console.WriteLine(contains);
    }
}

Contains with string value

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"};
        bool contains = presidents.Contains("H");
        Console.WriteLine(contains);
    }
}

Contains with string value and IEqualityComparer

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MyStringifiedNumberComparer : IEqualityComparer<string> {
    public bool Equals(string x, string y) {
        return (Int32.Parse(x) == Int32.Parse(y));
    }
    public int GetHashCode(string obj) {
        return Int32.Parse(obj).ToString().GetHashCode();
    }
}
public class MainClass {
    public static void Main() {
        string[] stringifiedNums = {"001", "49", "017", "0080", "00027", "2" };
        bool contains = stringifiedNums.Contains("000271",new MyStringifiedNumberComparer());
        Console.WriteLine(contains);
    }
}

Use Contains to check the existance of an element

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
public class MainClass{
   public static void Main(){
       int[] numbers = { 2, 6, 1, 56, 102 };
       Console.WriteLine("Is there the number 102?");
       Console.Write(numbers.Contains(102) ? "Yes, there is" : "No, there isn"t");
   }
}