Don't know how to loop through (n) number of nested objects in C#

Question

I looked at this article to see if I could use that as a starting point, but I don't see it addressing my particular problem. C#: N For Loops

I have the following code:

int criteriaCount = rule.SearchCriteria.Criteria.Count();
string criteria = "";
        for (int i = 0; i < criteriaCount; i++)
        {
            if (rule.SearchCriteria.Criteria[i].Criteria.Count() > 0)
            {
                criteria += string.Format("({0}" + System.Environment.NewLine, rule.SearchCriteria.Criteria[i].Display);
                criteria += string.Format("{0})" + System.Environment.NewLine, rule.SearchCriteria.Criteria[i].Criteria[i].Display);
            }
            else
            {
                criteria += string.Format("[{0}]" + System.Environment.NewLine, rule.SearchCriteria.Criteria[i].Display);
            }
        }

To explain a little, you have in SearchCriteria and Array of Criteria[]. I can loop through this and grab the follow I need from each Criteria object as you can see I am doing.

I am also looking at the second level deep, so SearchCriteria.Criteria[n].Criteria[n] and I can put a for loop their and grab any nested values there as well.

The part I cannot figure out is how can I account for a variable number of nested Criteria objects? I could potentially have this:

SearchCriteria.Criteria[n].Criteria[n] ... (repeat a hundred times)... .Criteria[n]

So it can have potentially an infinite number of nested objects, and an infinite number of sibling objects (Criteria[0], Criteria[1] ... Criteria[100000] is what I mean).

Is there a way I can loop through all this? I have heard the a recursive loop may be the answer, and I vaguely understand that concept, but what I don't know is how can I get the number of children and siblings?

Please, store the value of `Count()` into a variable... you don't need to call it so often when you are in no danger of modifying the contents. — TheZ, Aug 10 '12 at 20:33
Changed the code, this is just a rough, trying to get it to work sample, thus me just calling it every time. — ledgeJumper, Aug 10 '12 at 20:35

score 5 · Answer 1 · answered Aug 10 '12 at 20:37

The basic concept for a recursive loop is defined below. You will be limited to the space available on the stack.

private String GetSearchCriteria(Citeria root) {

  String result = root.Display;

  foreach (Criteria child in root.Criteria) {
    result += GetSearchCriteria(child);
  }

  return result;

}

score 2 · Accepted Answer · answered Aug 10 '12 at 20:44

Use recursion, and in your case you may use something like this...

        private static string DisplayCriteria(Criteria criteriaObject)
        {
            string criteria = "";
            foreach(Criteria c in criteriaObject)
            {
                if (c.Criteria.Count() > 0)
                {
                    criteria += string.Format("({0}" + System.Environment.NewLine, c.Display);
                    criteria += string.Format("{0})" + System.Environment.NewLine, DisplayCriteria(c.Criteria));
                }
                else
                {
                    criteria += string.Format("[{0}]" + System.Environment.NewLine, c.Display);
                }
            }
            return criteria;
        }

        // your code  ...
        DisplayCriteria(rule.SearchCriteria.Criteria);
        // your code  ...

I am not sure about the new lines there, you can add/remove them later

Thanks, this one actually makes the most sense to me. Gonna have to sit down and go through it all since my brain is having difficulties grasping what I need to do here. I kind of get it, I just need to think through how to recursive go through all the children and siblings, and what order to do that. Great start though, thanks! — ledgeJumper, Aug 10 '12 at 21:06

score 1 · Answer 3 · answered Aug 10 '12 at 20:45

You need to make your method into a "Recursive Method"...a method that calls itself to handle unlimited nesting, such as this:

public string ParseCriteria( Criteria criteria ) {
    string result = "(";
    result += criteria.Display;
    foreach( var criteria in criteria.Criteria) {
        result += ParseCriteria( criteria )
    }
    return result;
}

then, something like this in your existing code.

foreach( var criteria in rule.SearchCriteria.Criteria ) {
    string result += ParseCriteria(criteria);
}

string concatentation is not ideal, and my exmaple doesn't format correctly...but hopefully you get the idea.

Don't know how to loop through (n) number of nested objects in C#

3 Answers3