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Can I use yield return when the return type is an IGrouping<TKey, TElement> or an IDictionary<TKey, TValue>?
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When a yield return statement is reached in the iterator method, expression is returned, and the current location in code is retained. Execution is restarted from that location the next time that the iterator function is called.
IEnumerable has just one method called GetEnumerator. This method returns another type which is an interface that interface is IEnumerator. If we want to implement enumerator logic in any collection class, it needs to implement IEnumerable interface (either generic or non-generic).
The yield return statement returns one element at a time. The return type of yield keyword is either IEnumerable or IEnumerator . The yield break statement is used to end the iteration. We can consume the iterator method that contains a yield return statement either by using foreach loop or LINQ query.
The only difference between yield and return is whenever yield statement is encountered in a function, the execution of function is suspended and a value is send back to the caller but because of yield whenever the function is called again, the execution of function begin where it left off previously.
yield return works for exactly 4 cases:
IEnumerableIEnumerable<T>IEnumeratorIEnumerator<T>This is because it has to build a state machine internally; a dictionary (etc) wouldn't be possible with this. You can of course just return a suitable type instead.
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