Example of creating a custom delegate, Func types and lambda expressions

delegates.cs

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

namespace ScratchPad
{
    public static class Program
    {
        // Create a custom delegate
        public delegate int MyCustomDelegate(int value);

        // An example of an extension method for integer datatypes
        public static void Print(this int value)
        {
            // Print the value to the console e.g. 10.Print() would print "10\n"
            Console.WriteLine(value);
        }

        // An example of an extension method using a predicate (function that returns true or false)
        // The first parameter is either a list or array e.g. a type that inherits from IEnumerable
        public static bool HasValue<T>(this IEnumerable<T> source, Predicate<T> predicate)
        {
            foreach (var value in source)
            {
                if (predicate(value))
                {
                    return true;
                }
            }

            return false;
        }

        private static void Main()
        {
            // Print the value
            10000000.Print();

            // Use the custom delegate to create a predicate function
            MyCustomDelegate predicate = i => i * 2;
            Console.WriteLine(predicate(100));

            string[] array = { "10", "11", "12", "13", "14" };

            // Example of the .NET extension method .Any()
            var hasValue = array.HasValue(s => s == "10");
            Console.WriteLine(hasValue);

            // Example of using LINQ
            var items = new List<string>
            {
                "String 1",
                "String 2",
                "",
                "String 3",
                null,
                "String 4"
            };

            // Iterate over the the following items that aren't null or empty
            foreach (var item in items.Where(item => !String.IsNullOrEmpty(item)))
            {
                Console.WriteLine(item);
            }

            // Create a delegate function with 2 integer params and a boolean return
            Func<int, int, bool> example = (a, b) => a == b;
            Console.WriteLine(example(10, 10));

            // Example of using a Lambda expression and predefined method
            Func<int, string> someMethod = x => (100 * x).ToString();
            Console.WriteLine(someMethod(100));

            Console.WriteLine("Enter any key to continue. . .");

            Console.ReadKey(true);
        }
    }
}