Csharp/CSharp Tutorial/LINQ/Func

Accumulator function

<source lang="csharp">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));
       }
   }</source>

Add extension to Func

<source lang="csharp">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)); 
       }
   }</source>

Build the necessary Func<> delegates using anonymous methods

<source lang="csharp">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);
       }
   }</source>

Double recursive extension

<source lang="csharp">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));
       }
   }</source>

Lambda Expression for Func

<source lang="csharp">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));
       }
   }</source>

Lambda Expression to retrieve string length

<source lang="csharp">using System; using System.ruponentModel;

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

Overloading By Delegate Return Type

<source lang="csharp">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);
       }
   }</source>

Pass the delegates into the methods of Sequence

<source lang="csharp">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);
       }
   }</source>