How Can LINQ Efficiently Flatten Hierarchical Data and Filter by a Specific Property Value?

Use Linq flat level data

In the tree -like data structure, the flat list of nodes is often required from the nested level. For example, consider a "MyNode" object with the "Elements" attribute, which contains a sub -node collection. In order to obtain a flat list with all nodes with specific attribute values, Linq provides an elegant solution.

Solution

To flatten the tree in a Linq query and screen the specific attribute value, please follow the steps below:

The following is a detailed explanation:

<code class="language-csharp">// 扁平化树
IEnumerable<mynode> flatTree = e.SelectMany(c => Flatten(c.Elements)).Concat(new[] { e });

// 按属性值筛选扁平化列表
var result = flatTree.Where(n => n.group == 1);</code>

Flatten (C.ELEMENTS):

This part of the sub -node of each node in the original collection of recursively.

• Concat (new [] {e}): This attach the current node to the flat sub -node list.
Where (n = & gt; n.group == 1):
• This clause screens flat list, which only includes nodes with "group" values.
Extended method version
• In order to improve the readability of code, you can convert the flat function to expansion method:

The generic version of the custom tree

For trees that are different from "MyNode", you can use the generic version of the flat function. This version uses a function to retrieve the node:

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

Example usage

To flatten the "MyNode" tree and screen the node of "group" equal to 1:

By understanding the flat concept of tree and the strong operation of Linq, you can efficiently extract and operate data from the complex hierarchical structure.

<code class="language-csharp">public static IEnumerable<T> Flatten<T>(
    this IEnumerable<T> e,
    Func<T, IEnumerable<T>> f
) => e.SelectMany(c => f(c).Flatten(f)).Concat(e);</code>

The above is the detailed content of How Can LINQ Efficiently Flatten Hierarchical Data and Filter by a Specific Property Value?. For more information, please follow other related articles on the PHP Chinese website!