Csharp/CSharp Tutorial/Data Structure/yield

Simple Iterator

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
    class Program
    {
        public static IEnumerable SimpleList()
        {
            yield return "string 1";
            yield return "string 2";
            yield return "string 3";
        }
        public static void Main(string[] args)
        {
            foreach (string item in SimpleList())
                Console.WriteLine(item);
        }
    }

Skip the foreach and manually use the enumerable and enumerator for a "yield" IEnumerable

using System;
using System.Collections.Generic; 
class LetterCollection
{
   string[] letters ={ "A", "B", "C"};
   
   public IEnumerable<string> Forward()                       
   {
      for (int i = 0; i < letters.Length; i++)
         yield return letters[i];
   }
}
class MainClass
{
   static void Main()
   {
      LetterCollection cc = new LetterCollection();
      
      IEnumerable<string> ieable = cc.Forward();
      IEnumerator<string> ieator = ieable.GetEnumerator();
      while (ieator.MoveNext())
         Console.Write("{0} ", ieator.Current);
   }
}

A B C

Use multiple yield statements

using System; 
using System.Collections; 
 
class MyClass { 
  public IEnumerator GetEnumerator() { 
    yield return "A"; 
    yield return "B"; 
    yield return "C"; 
    yield return "D"; 
    yield return "E"; 
  } 
} 
 
class MainClass { 
  public static void Main() { 
    MyClass mc = new MyClass(); 
 
    foreach(char ch in mc) 
      Console.Write(ch + " "); 
 
    Console.WriteLine(); 
  } 
}

A B C D E

Use yield break

using System; 
using System.Collections; 
 
class MyClass { 
  char ch = "A"; 
 
  public IEnumerator GetEnumerator() { 
    for(int i=0; i < 26; i++) { 
      if(i == 10) 
         yield break; // stop iterator early 
      yield return (char) (ch + i); 
    } 
  } 
} 
 
class MainClass { 
  public static void Main() { 
    MyClass mc = new MyClass(); 
 
    foreach(char ch in mc) 
      Console.Write(ch + " "); 
 
    Console.WriteLine(); 
  } 
}

A B C D E F G H I J

Yield Break And Try Finally

using System;
using System.Collections.Generic;
using System.Threading;
using System.ruponentModel;
    class MainClass{
        static IEnumerable<int> CountWithTimeLimit(DateTime limit){
            try{
                for (int i = 1; i <= 5; i++){
                    if (DateTime.Now >= limit){
                        yield break;
                    }
                    yield return i;
                }
            }finally{
                Console.WriteLine("Stopping!");
            }
        }
        static void Main(){
            DateTime stop = DateTime.Now.AddSeconds(20);
            foreach (int i in CountWithTimeLimit(stop))
            {
                Console.WriteLine("Received {0}", i);
                Thread.Sleep(100);
            }
        }
    }

yield IEnumerable data

using System;
using System.Collections.Generic; 
class LetterCollection
{
   string[] letters ={ "A", "B", "C"};
   
   public IEnumerable<string> Forward()                       
   {
      for (int i = 0; i < letters.Length; i++)
         yield return letters[i];
   }
}
class MainClass
{
   static void Main()
   {
      LetterCollection cc = new LetterCollection();
      foreach (string color in cc.Forward())
         Console.Write("{0} ", color);
      Console.WriteLine("");
   }
}

A B C

Yield with Break

using System;
using System.Collections.Generic;
using System.Threading;
using System.ruponentModel;
    class MainClass
    {
        static IEnumerable<int> CountWithTimeLimit(DateTime limit)
        {
            for (int i = 1; i <= 5; i++)
            {
                if (DateTime.Now >= limit)
                {
                    yield break;
                }
                yield return i;
            }
        }
        static void Main()
        {
            DateTime stop = DateTime.Now.AddSeconds(2);
            foreach (int i in CountWithTimeLimit(stop))
            {
                Console.WriteLine("Received {0}", i);
                Thread.Sleep(100);
            }
        }
    }