Csharp/CSharp Tutorial/LINQ/Func

Accumulator function

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
    class MainClass
    {
        static void Main()
        {
            Func<int, Func<int, int>> accumulatorGenerator = (n => (i => n += i+8));
            var accumulator = accumulatorGenerator(1);
            Console.WriteLine(accumulator(1));
        }
    }

Add extension to Func

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
    static class CurryingExtensions
    {
        public static Func<A, Func<B, R>> myExt<A, B, R>(this Func<A, B, R> f)
        {
            return a => b => f(a, b);
        }
    }
    class MainClass
    {
        static void Main()
        {
            Func<int, int, int> adder = (x, y) => (x + y);
            Func<int, Func<int, int>> c = adder.myExt();
            Func<int, int> addsTwo = c(2);
            Console.WriteLine(addsTwo(5)); 
        }
    }

Build the necessary Func<> delegates using anonymous methods

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml.Linq;
using System.Linq;
    class Program
    {
        static void Main(string[] args)
        {
            string[] currentVideoGames = {"test", "this is a test", "asdf", "game 1","game 2", "game 3"};
            Func<string, bool> searchFilter = delegate(string game) { return game.Length > 6; };
            Func<string, string> itemToProcess = delegate(string s) { return s; };
            var subset = currentVideoGames
                .Where(searchFilter).OrderBy(itemToProcess).Select(itemToProcess);
            // Print out the results.
            foreach (var game in subset)
                Console.WriteLine("Item: {0}", game);
        }
    }

Double recursive extension

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
    static class DoubleApplicationExtensions
    {
        public static Func<T, T> ApplyTwice<T>(this Func<T, T> original)
        {
            return x => original(original(x));
        }
    }
    class MainClass
    {
        static void Main()
        {
            Func<int, int> incrementer = x => x + x;
            Func<int, int> doubleIncrementer = incrementer.ApplyTwice();
            Console.WriteLine(doubleIncrementer(5));
        }
    }

Lambda Expression for Func

using System;
using System.Collections.Generic;
using System.Text;
using System.ruponentModel;

    class LambdaExpression
    {
        static void Main()
        {
            Func<int, int, string> func = (x, y) => (x * y).ToString();
            Console.WriteLine(func(5, 20));
        }
    }

Lambda Expression to retrieve string length

using System;
using System.ruponentModel;
    class MainClass
    {
        static void Main()
        {
            Func<string, int> returnLength = (string text) => { return text.Length; };
            Console.WriteLine(returnLength("Hello"));
        }
    }

Overloading By Delegate Return Type

using System;
using System.ruponentModel;
    class MainClass
    {
        static void Execute(Func<int> action)
        {
            Console.WriteLine("action returns an int: " + action());
        }
        static void Execute(Func<double> action)
        {
            Console.WriteLine("action returns a double: " + action());
        }
        static void Main()
        {
            Execute(() => 1);
        }
    }

Pass the delegates into the methods of Sequence

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml.Linq;
using System.Linq;
    class Program
    {
        static void Main(string[] args)
        {
            string[] currentVideoGames = {"test", "this is a test", 
                          "asdf", "game 1",
                          "game 2", "game 3"};
            Func<string, bool> searchFilter = delegate(string game) { return game.Length > 6; };
            Func<string, string> itemToProcess = delegate(string s) { return s; };
            var subset = currentVideoGames
                .Where(searchFilter).OrderBy(itemToProcess).Select(itemToProcess);
            foreach (var game in subset)
                Console.WriteLine("Item: {0}", game);
        }
    }