C# 2.0 Yield Return Iterator

One interesting new feature of the C# 2.0 is the "yield" keyword.  Basically it is used to iterate through objects returned by a method. It creates a state engine in IL so you can create methods that retain their state and dont have to go through the pain of maintaining state in your code.

Here is a simple example that demonstrates how yield return can be used to maintain state in a method. Every time you call GetInt() you will receive a new incremented integer.

public static IEnumerable<int> GetInt() {    for (int i = 0; i < 5; i++)        yield return i; }

Here's the implementation.

class Program {         static void Main(string[] args)         {             foreach (int i in GetInt())                 Console.WriteLine("Got " + i.ToString());         }         public static IEnumerable<int> GetInt()         {             for (int i = 0; i < 5; i++)                 yield return i;         } }

Usually, the "yield" keyword will be useful when you implement the GetEnumerator() method of the IEnumerable interface

class TestClass: IEnumerable<int> {         #region IEnumerable<int> Members         public IEnumerator<int> GetEnumerator()         {             for (int i = 0; i < 5; i++)                 yield return i;         }         #endregion         #region IEnumerable Members         IEnumerator IEnumerable.GetEnumerator()         {             return GetEnumerator();         }         #endregion }

Hopefully, this brief sample has helped you understand the new "yield" keyword and how it can be used.

Until next time,

Happy coding