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