//What is the use of yeild keyword
public static void YieldKeywordExplanation()
{
// 1. yield keyword helps to do custom/statefull iteration over a collection
// 2. When we use yield keyword, the control moves between source and caller.
//Custom Iteration example without using temp collection
Questions questions = new Questions();
Console.Write("Number greater than 3 are:");
foreach (int number in questions.Filter())
{
Console.Write(" {0} ", number);
}
//Statefull iteration example
//For e.g, we want to display the running total of a list
Console.WriteLine();
Console.Write("Running total are:");
foreach (int runningTotal in questions.RunningTotal())
{
Console.Write(" {0} ", runningTotal);
}
// 3. yield keyword effectively creates a lazy enumeration over collection items that can be much more efficient.
// For example, yield return is a .NET sugar to return an IEnumerable with the only needed items.
// Code without yield:
//class MyItem
//{
//public MyItem() { }
//static public IEnumerable CreateListOfItems()
//{
// return new List {
// new MyItem(),
// new MyItem(),
// new MyItem() };
//}
//}
//Same code using yield:
//class MyItem
//{
//public MyItem() { }
//static public IEnumerable CreateListOfItems()
//{
//yield return new MyItem();
//yield return new MyItem();
//yield return new MyItem();
//}
//}
// The advantage of using yield is that if the function consuming your data simply needs the first item of the collection,
// the rest of the items won’t be created so it’s more efficient.
// 4. The yield operator allows the creation of items as it is demanded.That’s a good reason to use it.
// 5. The declaration of an iterator must meet the following requirements:
// 5.A. The return type must be IEnumerable, IEnumerable<T>, IEnumerator, or IEnumerator<T>.
// 5.B. The declaration can't have any in ref or out parameters.
// 6. The yield type of an iterator that returns IEnumerable or IEnumerator is object.
// 7. If the iterator returns IEnumerable<T> or IEnumerator<T>, there must be an implicit conversion from the type of the expression in the yield return statement to the generic type parameter.
// 8. You can't include a yield return or yield break statement in:
// 8.A. Lambda expressions and anonymous methods.
// 8.B. Methods that contain unsafe blocks.
// 9. A yield return statement can't be located in a try-catch block. A yield return statement can be located in the try block of a try-finally statement.
// 10. A yield break statement can be located in a try block or a catch block but not a finally block.
// 11. If the foreach body(outside of the iterator method) throws an exception, a finally block in the iterator method is executed.
// 12. yield keyword can be used in a get accessor that is an iterator.
var theGalaxies = new Galaxies();
foreach (Galaxy theGalaxy in theGalaxies.NextGalaxy)
{
Console.WriteLine("Galaxy name: {0} and Mega Light Year is: {1}", theGalaxy.Name, theGalaxy.MegaLightYears);
}
// 13. You can use a yield break statement to end the iteration.
}
static void Main(string[] args)
{
Questions.PrintOrgEmployeeHirechy();
Console.ReadKey();
}
