How to code variable loop level in foreach in List

Question

I have the following class:

class Person 
{
    public string Name { get; set; }
    public List<Person> Children { get; set; } 
}

And I created an instance of this class, fox ex.

Person pers = new Person();

I can code foreach loops statically and store the Children in some list:

foreach (var item in pers.Children)
{
    List<Person> r = item.Children;
    foreach (var item2 in item.Children)
    {
        List<Person> k = item2.Children;
        foreach (var item3 in item2.Children)
        {
        etc..
        }
    }
}

The problem is, how to code the foreach loops, if the "pers" has a children, and one of his children (pers.Children) also has a children. It's something like genealogical tree.

I mean, how to make it more dynamically? Because I don't know how the structure of the family can be.

Edit: I just want to show all the successors of one person. For example just names of his successors

You can solve it recursivelly but you should describe what you actually want to perform with this genealogical tree in order to get specific answers. — JuniorCompressor, Apr 18 '15 at 11:55
What are you trying to achieve with the deep childrens list? Recuresivity is what you need... but how? I can't help as far as I don't know what you are trying to fulfil. — tmarwen, Apr 18 '15 at 11:56
I just want to show all the successors of one person. For example just names of his successors — kamyk, Apr 18 '15 at 11:58

score 2 · Accepted Answer · answered Apr 18 '15 at 12:07

2

Use recursion :

public static void ShowAll(Person pers)
{
    Console.WriteLine(pers.Name);
    foreach (var item in pers.Children)
    {
        ShowAll(item);
    }
}

answered Apr 18 '15 at 12:07

Guillaume

12,824
3
40
48

score 1 · Answer 2 · answered Apr 18 '15 at 14:21

Another way you can do this is to add a method to your class which will show the person's name (and/or other data) and then display their children's names (and/or other data) by calling the method on each child instance.

The nice thing about this approach is that it makes your code much cleaner and leaves it to the Person class to handle how it displays itself (and it's successors).

Here's an example of your class modified with such a method:

public class Person
{
    public string Name { get; set; }
    public List<Person> Children { get; set; }

    public Person()
    {
        Children = new List<Person>();
    }

    public void DisplaySuccessors(int indendationLevel = 0)
    {
        Console.WriteLine("{0}{1}", new String('.', indendationLevel * 2), Name);

        foreach (var child in Children)
        {
            child.DisplaySuccessors(indendationLevel + 1);
        }
    }
}

And here's how you could use it:

private static void Main()
{
    var mother = new Person {Name = "Mother"};

    var daughter1 = new Person {Name = "daughter1"};
    var granddaughter1 = new Person { Name = "granddaughter1" };

    var son1 = new Person { Name = "son1" };
    var grandson1 = new Person { Name = "grandson1" };
    var granddaughter2 = new Person { Name = "granddaughter2" };

    mother.Children.Add(daughter1);
    mother.Children.Add(son1);
    daughter1.Children.Add(granddaughter1);
    son1.Children.Add(grandson1);
    son1.Children.Add(granddaughter2);

    mother.DisplaySuccessors();
}

Output:

Mother
..daughter1
....granddaughter1
..son1
....grandson1
....granddaughter2

score 0 · Answer 3 · edited May 23 '17 at 12:17

0

Handling tree like data structures has already been intensively discussed: Tree Data Structure

edited May 23 '17 at 12:17

Community

1
1

answered Apr 18 '15 at 12:02

Michael Sander

2,677
23
29

score 0 · Answer 4 · answered Apr 18 '15 at 12:07

One way is recursion, like this method which calls itself:

static void WriteAllSuccessors(Person pers, int depth = 0)
{
  var indent = new string(' ', depth * 4);
  Console.WriteLine(indent + pers.Name);
  foreach (var child in pers.Children)
      WriteAllSuccessors(child, depth + 1);
}

Note the indentation.

score 0 · Answer 5 · answered Apr 18 '15 at 12:20

This is standard recursion, where you call itself and add nodes to some list:

static void Main(string[] args)
        {
            List<Person> successors = new List<Person>();

            var person = new Person()
            {
                Name = "GrandFather",
                Children = new List<Person>()
                {
                    new Person()
                    {
                        Name = "Son",
                        Children = new List<Person>()
                        {
                            new Person()
                            {
                                Name = "SonOfSon"
                            }

                        }
                    },
                    new Person()
                    {
                        Name = "Daughter",
                        Children = new List<Person>()
                        {
                            new Person()
                            {
                                Name = "DaughterOfDaughter"
                            }
                        }
                    }
                }
            };

            SearchForSuccessors(person.Children, successors);
        }

        public static void SearchForSuccessors(List<Person> persons, List<Person> successors)
        {
            foreach(var person in persons )
            {
                successors.Add(person);

                if (person.Children != null)
                    SearchForSuccessors(person.Children, successors);
            }
        }

How to code variable loop level in foreach in List

5 Answers5