C # iterate over recursive lists of nested properties

Question

foreach (TargetObject innerObject1 in complexObject.InnerObjects) { foreach (TargetObject innerObject2 in innerObject1.InnerObjects) { foreach (TargetObject innerObject3 in innerObject2.InnerObjects) { yield return innerObject3; } yield return innerObject2; } yield return innerObject1; } 

How can I do it fast? I need to collect all TargetObject instances placed in these nested lists into one list. Here is an attempt that did not work.

  public static IEnumerable<TargetObject> GetRecursively(params TargetObject[] startingObjects) { foreach (TargetObject startingObject in startingObjects) { foreach (TargetObject innerObject in GetRecursively(startingObject.InnerObjects.ToArray())) { yield return innerObject; } yield return startingObject; } } 

Answer 1

Similarly, output startObject and call recursively for each element in InnerObjects :

 public static IEnumerable<TargetObject> GetRecursively(TargetObject startingObject) { yield return startingObject; if (startingObject.InnerObjects != null) foreach (TargetObject innerObject in startingObject.InnerObjects.ToArray()) foreach (TargetObject recursiveInner in GetRecursively(innerObject)) yield return recursiveInner; } 

To maintain an array as a parameter, wrap a foreach around it:

 public static IEnumerable<TargetObject> GetRecursively2(params TargetObject[] startingObjects) { foreach (TargetObject startingObject in startingObjects) { yield return startingObject; if (startingObject.InnerObjects != null) foreach (TargetObject innerObject in startingObject.InnerObjects.ToArray()) foreach (TargetObject recursiveInner in GetRecursively(innerObject)) yield return recursiveInner; } }