How to Flatten a Hierarchical Tree Structure into a Flat List Using LINQ?

The structure of the flat display of linq

Assume that there is a layered tree data structure represented by the

class, each of which has a parent node, a sub -node collection, and a group of identifier. Essence

MyNode Challenge

The goal is to obtain a list of all objects, including parent nodes and sub -nodes, as a single flat list. However, only nodes should be included in the results list.

Solution MyNode group == 1

In order to achieve this flattelling, the following Linq expression can be used:

This expression is recursive throughout the tree structure, and the exhibition is flattened as a single list. It selects all sub -nodes of the given node and calls

to generate recursively. Then connect this sequence to the current node to generate the merger table.

Filter

<code class="language-csharp">IEnumerable<MyNode> Flatten(IEnumerable<MyNode> e) =>
    e.SelectMany(c => Flatten(c.Elements)).Concat(e);</code>

Flatten Once the tree is flattened, you can use the

method filter list, and only select the node of

.

The additional style enhancement

Where(...) group == 1 In order to improve readability,

Method can be defined as an extension function in static class:

<code class="language-csharp">var result = flattenedNodes.Where(n => n.group == 1);</code>

Found implementation

In order to generalize the flat process, it can create a generic expansion method. It accepts a tree structure and a function to generate off the offspring from the node: Flatten

<code class="language-csharp">public static IEnumerable<MyNode> Flatten(this IEnumerable<MyNode> e) =>
    e.SelectMany(c => c.Elements.Flatten()).Concat(e);</code>

This method allows the exhibition to flatten any layered data structure, provided that a function is defined to retrieve off the offspring nodes from each element.

To implement this generic type, just call the method and provide the corresponding functions to extract the offspring:

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