The yield keyword in C# is used to create an iterator method that allows you to iterate over a collection one item at a time, rather than returning the entire collection at once[1][2][3][4]. It is particularly useful when working with large collections of data, as it allows you to process the data incrementally without having to load the entire collection into memory[2].
Here's how the yield keyword works:
You define a method that returns an IEnumerable or IEnumerator and use the yield return statement to return each item in the collection[1][3].
When the method is called, the compiler generates a state machine that keeps track of the current position in the iteration[3].
Each time yield return is encountered, the current state is saved, and the method returns the yielded value to the caller[1][4].
On subsequent calls, the method resumes from the saved state, continuing the iteration until the next yield return or yield break statement is reached[1][4].
