What is Yield Keyword in C#

Followings are the important points on the Yield Keyword of C-Sharp:

• Yield is Contextual Keyword in C#, it is used to indicate a method as an iterator in which yield keyword is used.
•  It helps developer to avoid writing another method for holding the state of iteration.
• Yield keyword is used along with "return" & "break", see the following two usage of Yield keyword:

Syntax of Yield in C#:

1. yield return <return Value>; 

2. yield break;

• Following is the example of "Yield" keyword:

1.     class Program
2.     {
3.         static void Main(string[] args)
4.         {
5.             foreach (var i in GetData())
6.             {
7.                 Console.WriteLine(i.ToString());
8.             }
9.             Console.ReadLine();
10.         }
11. 
    
12.         static IEnumerable<string> GetData()
13.         {
14.             yield return "A";
15.             yield return "B";
16.             yield return "C";
17.             yield return "D";
18.             yield return "E";
19.         }
20.     }
21.    OUTPUT:
22.    A
23.    B
24.    C
25.    D
26.    E

• From the above example, it returns the value when it reaches "yield return" & it stops the iteration and control goes back to calling method & in the next iteration, it starts from the same place, it left in the last iteration. It continues to do the same till it reaches the end of the loop.
• The return type must be IEnumerable, IEnumerable<T>, IEnumerator, IEnumerator<T>
• Yield return can't be used in try-catch block, it can be used in try block of try-finally statement.
• Yield break can be used in try or catch block, but not in finally block