Deeply nested search through Document tree

Question

I have this code block, where I search for the value of Ordnungsbegriff. I have to search through a tree of my CurrentDocument.

How can I rewrite it to be more dynamic? I don't know at which level I will find my value.

string xy = ""; 
try
{
 if (string.IsNullOrEmpty(CurrentDocument.Ordnungsbegriff))
 {
 if (string.IsNullOrEmpty(CurrentDocument.ParentDocument.Ordnungsbegriff))
 {
 if (string.IsNullOrEmpty(CurrentDocument.ParentDocument.ParentDocument.Ordnungsbegriff))
 {
 if (string.IsNullOrEmpty(CurrentDocument.ParentDocument.ParentDocument.ParentDocument.Ordnungsbegriff))
 {
 if (string.IsNullOrEmpty(CurrentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.Ordnungsbegriff))
 {
 if (string.IsNullOrEmpty(CurrentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.Ordnungsbegriff))
 {
 if (string.IsNullOrEmpty(CurrentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.Ordnungsbegriff))
 {
 xy = "Nach 6. Ebene, Suche abgebrochen.";
 }
 else
 xy = CurrentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.Ordnungsbegriff;
 }
 else
 xy = CurrentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.Ordnungsbegriff;
 }
 else
 xy = CurrentDocument.ParentDocument.ParentDocument.ParentDocument.ParentDocument.Ordnungsbegriff;
 }
 else
 xy = CurrentDocument.ParentDocument.ParentDocument.ParentDocument.Ordnungsbegriff;
 }
 else
 xy = CurrentDocument.ParentDocument.ParentDocument.Ordnungsbegriff;
 }
 else
 xy = CurrentDocument.ParentDocument.Ordnungsbegriff;
 }
 else
 xy = CurrentDocument.Ordnungsbegriff;
}
catch (Exception)
{
 xy = "Fehler in Suche";
}

• Legato: Welcome to CodeReview. What exactly do you mean by "I don't know at which level I find my value." Is this your code?
• Al Salvador: Yes, this is my code. I have CurrentDocument.Ordnungsbegriff, if this is null then i search at CurrentDocument.ParentDocument.Ordnungsbegriff and so on, until i find a value for Ordnungsbegriff

Answer 1

I find recursion complicated You can use a while loop:

private string SearchDocument(Document doc)
{
 while (doc != null) 
 {
 if (!string.IsNullOrEmpty(doc.Ordnungsbegriff))
 {
 return doc.Ordnungsbegriff;
 }
 doc = doc.ParentDocument;
 }
 return null;
}

Edit: As a further point - it's better not to mix languages in your code: Ordnungsbegriff should be Keyword (according to Google).

• RubberDuck: A very nice alternative. I hadn't considered an iterative approach.

Answer 2

Recursion. You need some recursion friend.

Create a function that returns the value if it's found or calls itself on the next level if it's not found. This may not be a 100% working solution, because I don't have quite enough context for that, but it should give you a good start.

private string SearchDocument(Document doc)
{
 if (doc == null)
 {
 return "Nach 6. Ebene, Suche abgebrochen.";
 }
 if (string.IsNullOrEmpty(doc.Ordnungsbegriff))
 {
 return SearchDocument(doc.ParentDocument);
 }
 return doc.Ordnungsbegriff
}

If you don't know much (or anything) about recursion, I recommend this video from Computerphile. It's a very good primer on the topic.

• RobH: Have you ever read the little schemer? It blew my mind then I forgot most of it but it's the closest I've ever come to being comfortable with recursion!
• RubberDuck: No, but I'm about to @RobH. =) It took me a while to get comfortable with recursion myself, but once you get it you get it. I really do recommend the video linked in my answer. It's a very good explination.

Answer 3

First of all, I really like RobH's solution. If you find that traversing the document hierarchy is a common operation in your code, consider introducing a method AncestorsAndSelf() to your Document class (alternatively, make it an extension method):

public IEnumerable<Document> AncestorsAndSelf()
{
 for (var document = this; document != null; document = document.ParentDocument)
 {
 yield return document;
 }
}

This will allow you to write the method in a more declarative way

private static string SearchDocument(Document document)
{
 return document.AncestorsAndSelf()
 .Select(d => d.Ordnungsbegriff)
 .FirstOrDefault(o => !string.IsNullOrEmpty(o));
}