IEnumerableTResult

IEnumerableTResult<TResult> is a generic interface used to model a sequence of results that can be enumerated while also carrying an associated final outcome. In common designs, it extends IEnumerable<TResult> and adds a property TResult Result { get; } that exposes a terminal value computed from the sequence. This combination supports streaming scenarios where items are consumed as they become available and the final result is obtained at the end.

Implementation details vary. Some implementations compute Result lazily as enumeration proceeds; others compute it after the last item is produced. Because it inherits from IEnumerable<TResult>, consumers can use standard foreach loops; however, many implementations are single-pass and should not be enumerated multiple times without reinitialization.

Common use cases include data processing pipelines, where each yielded element is processed immediately and a summary value summarizes the entire operation. It can also model operations that may fail but still yield intermediate results. When designing such an interface, care should be taken to document whether Result depends on enumeration order or on all items.

For example, a class that reads log entries and yields lines while computing a final status value as Result, such as OK or ERROR, depending on the content. Consumers can loop through items and finally inspect Result to determine overall outcome.

See also: IEnumerable, Result patterns, streaming interfaces.