How to search Hierarchical Data with Linq

Question

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) {

         


        

Answer 1

So, the simplest option is to write a function that traverses your hierarchy and produces a single sequence. This then goes at the start of your LINQ operations, e.g.

    IEnumerable Flatten(this T source)
    {
      foreach(var item in source) {
        yield item;
        foreach(var child in Flatten(item.Children)
          yield child;
      }
    }

To call simply: familyRoot.Flatten().Where(n => n.Name == "Bob");

A slight alternative would give you a way to quickly ignore a whole branch:

    IEnumerable Flatten(this T source, Func predicate)
    {
      foreach(var item in source) {
         if (predicate(item)) {          
            yield item;
            foreach(var child in Flatten(item.Children)
               yield child;
      }
    }

Then you could do things like: family.Flatten(n => n.Children.Count > 2).Where(...)