Greg Gum Greg Gum - 1 year ago 93
C# Question

How to search Hierarchical Data with Linq

I need to search a tree for data that could be anywhere in the tree. How can this be done with linq?

class Program
static void Main(string[] args) {

var familyRoot = new Family() {Name = "FamilyRoot"};

var familyB = new Family() {Name = "FamilyB"};

var familyC = new Family() {Name = "FamilyC"};

var familyD = new Family() {Name = "FamilyD"};

//There can be from 1 to n levels of families.
//Search all children, grandchildren, great grandchildren etc, for "FamilyD" and return the object.


public class Family {
public string Name { get; set; }
List<Family> _children = new List<Family>();

public List<Family> Children {
get { return _children; }

Answer Source

That's an extension to It'sNotALie.s answer.

public static class Linq
    public static IEnumerable<T> Flatten<T>(this T source, Func<T, IEnumerable<T>> selector)
        return selector(source).SelectMany(c => Flatten(c, selector))
                               .Concat(new[] { source });

Sample test usage:

var result = familyRoot.Flatten(x => x.Children).FirstOrDefault(x => x.Name == "FamilyD");

Returns familyD object.

You can make it work on IEnumerable<T> source too:

public static IEnumerable<T> Flatten<T>(this IEnumerable<T> source, Func<T, IEnumerable<T>> selector)
    return source.SelectMany(x => Flatten(x, selector))
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