C#•2y ago

❔ How to get all children of parent node?

I have a DTO as image. I want to get all children (included children of child) . How can I achive this ? Thanks

6 Replies

ero•2y ago

what children? i don't see any there

I think you'll need something like dbContext.Nodes.Where(node => node.ParentId == id) and then also do that for all of those children something like this

IEnumerable<Node> GetDescendants(Node node)
{
    var children = dbContext.Nodes.Where(n => n.ParentId == node.Id);
    return children.Concat(children.SelectMany(GetDescendants));
}

IEnumerable<Node> GetDescendants(Node node)
{
    var children = dbContext.Nodes.Where(n => n.ParentId == node.Id);
    return children.Concat(children.SelectMany(GetDescendants));
}

of course assuming you're using Entity Framework (or this isn't a database at all)

.perceptronOP•2y ago

{
    "data": [
        {
            "id": 2,
            "name": "General",
            "parentId": "0"
        },
        {
            "id": 3,
            "name": "Fruits",
            "parentId": "2"
        },
        {
            "id": 6,
            "name": "Vegetables",
            "parentId": "2"
        },
        {
            "id": 12,
            "name": "Apple",
            "parentId": "3"
        }
    ],
    "success": true,
    "messages": null
}

ero•2y ago

i see yeah you wanna do what thinkger suggested

SWEETPONY•2y ago

internal static class GenericHelpers
{
    public static IEnumerable<TreeItem<T>> GenerateTree<T, K>(
        this IEnumerable<T> collection,
        Func<T, K> idSelector,
        Func<T, K> parentIdSelector,
        K rootId = default( K ) )
    {
        foreach ( var c in collection.Where( c => EqualityComparer<K>.Default.Equals( parentIdSelector( c ), rootId ) ) )
        {
            yield return new TreeItem<T>
            {
                Item = c,
                Children = collection.GenerateTree( idSelector, parentIdSelector, idSelector( c ) )
            };
        }
    }
}

var root = yourCollection.GenerateTree(
            item=> item.Id, 
            item=> item.ParentId );

internal static class GenericHelpers
{
    public static IEnumerable<TreeItem<T>> GenerateTree<T, K>(
        this IEnumerable<T> collection,
        Func<T, K> idSelector,
        Func<T, K> parentIdSelector,
        K rootId = default( K ) )
    {
        foreach ( var c in collection.Where( c => EqualityComparer<K>.Default.Equals( parentIdSelector( c ), rootId ) ) )
        {
            yield return new TreeItem<T>
            {
                Item = c,
                Children = collection.GenerateTree( idSelector, parentIdSelector, idSelector( c ) )
            };
        }
    }
}

var root = yourCollection.GenerateTree(
            item=> item.Id, 
            item=> item.ParentId );

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ How to get all children of parent node?