C#•2y ago

How to generate a category tree

public class Category
{
    public int Id { get; set; }

    public Thread Thread { get; set; } = null!;
    public Guid ThreadId { get; set; }

    public string Name { get; set; } = string.Empty;
    public string Title { get; set; } = string.Empty;
    
    public ICollection<Category> Subcategories { get; set; } = new List<Category>();
    public int? CategoryId { get; set; }
}

public class Category
{
    public int Id { get; set; }

    public Thread Thread { get; set; } = null!;
    public Guid ThreadId { get; set; }

    public string Name { get; set; } = string.Empty;
    public string Title { get; set; } = string.Empty;
    
    public ICollection<Category> Subcategories { get; set; } = new List<Category>();
    public int? CategoryId { get; set; }
}

I have such categories, if we go down, i.e. Warzone2 -> DMZ -> Mission, then there is no problem. What if he wants to go up, with Mission ->DMZ -> Warzone2. How can I do it straight? The only thing that comes to my mind is foreach and each time checking if the element is generated correctly.

1 Reply

Alerin•2y ago

Or does anyone know how to google it?

    public List<Models.Category> Parents { get; set; } = new();

    public async Task GetParent(int id)
    {
        var p = await _context.Categories.SingleOrDefaultAsync(x => x.Id == id);
        if (p != null)
        {
            Parents.Add(p);
            if (p.CategoryId is not null)
                await GetParent(p.CategoryId ?? 0);
        }
    }

    public List<Models.Category> Parents { get; set; } = new();

    public async Task GetParent(int id)
    {
        var p = await _context.Categories.SingleOrDefaultAsync(x => x.Id == id);
        if (p != null)
        {
            Parents.Add(p);
            if (p.CategoryId is not null)
                await GetParent(p.CategoryId ?? 0);
        }
    }

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How to generate a category tree