Question

Given the following class, used to build a tree hierarchy:

public class simpletest
{
    public simpletest Parent { get; set; }
    public IList<simpletest> Children { get; set; }
    public string Name { get; set; }
}

How could I get a list of all objects for a specific level?

Here is some sample data (hopefully its formatted correctly):

var root = new simpletest() { Name = "Root" };
var level1childA = new simpletest() { Name = "level1childA", Parent = root };
var level1childB = new simpletest() { Name = "level1childB", Parent = root };

var level2childA = new simpletest() { Name = "level2childA", Parent = level1childA };
var level2childB = new simpletest() { Name = "level2childB", Parent = level1childA };
var level2childC = new simpletest() { Name = "level2childC", Parent = level1childB };
var level2childD = new simpletest() { Name = "level3childD", Parent = level1childB };

var level3childA = new simpletest() { Name = "level3childA", Parent = level2childA };
var level3childB = new simpletest() { Name = "level3childB", Parent = level2childA };
var level3childC = new simpletest() { Name = "level3childC", Parent = level2childB };
var level3childD = new simpletest() { Name = "level3childD", Parent = level2childB };
var level3childE = new simpletest() { Name = "level3childE", Parent = level2childC };
var level3childF = new simpletest() { Name = "level3childF", Parent = level2childC };
var level3childG = new simpletest() { Name = "level3childG", Parent = level3childD };
var level3childH = new simpletest() { Name = "level3childH", Parent = level3childD };

level2childA.Children = new List<simpletest> { level3childA, level3childB };
level2childB.Children = new List<simpletest> { level3childC, level3childD };
level2childC.Children = new List<simpletest> { level3childE, level3childF };
level2childD.Children = new List<simpletest> { level3childG, level3childH };

level1childA.Children = new List<simpletest> { level2childA, level2childB };
level1childB.Children = new List<simpletest> { level2childC, level2childD };

So for example, using node level3childE, how would I get all the nodes from the same level? The node names can be anything.

Answer 1

Here’s an (untested) recursive approach implemented as a member function of simpletest:

IEnumerable<simpletest> ElementsAtDepth(int depth) {
    if(depth > 0) {
        foreach(simpletest child in this.Children)
            foreach(simpletest element in child.ElementsAtDepth(depth - 1))
                yield return element;
    }
    else {
        foreach(simpletest element in this.Children)
            yield return element;
    }
}