How to make multilevel menu from categories

See more:

ASP.NET

MVC5

Hi I have an categories model that can have multiple subcategories. I want to show those categories in my menu, but can only get one level down. How do I make an multilevel menu soloution?
I have tried with an helper method inside the partial view, but it loads it double.

The Category model :

public class Category
    {
        public int CategoryId { get; set; }
        [Required(ErrorMessage = "Fill in a Name")]
        public string Name { get; set; }
        public int? ParentCategoryId { get; set; }
        public Category ParentCategory { get; set; }
        public virtual ICollection Listings { get; set; }
    }

CategoriesController that fill the partial view _Menu

[ChildActionOnly]
       public ActionResult GetMenu()
       {
           IList<Category> catAll = new List<Category>();
           catAll = categoriesRepository.All.ToList();
           return PartialView("_Menu", catAll);
       }

The Partial view _Menu

@model List
    @foreach (var mp in Model.Where(p => p.ParentCategoryId == null))
    {
       
            @mp.Name
            
                @foreach (var menuLevel2 in Model.Where(p => p.ParentCategoryId.Equals(mp.CategoryId)))
                {
                    @menuLevel2.Name                 
                            @ShowTree(Model, mp.CategoryId);                    
                    }
                }
            
        
    }
    @helper ShowTree(List foos, int ParentId)
    {
foreach (var menuLevel2 in foos)
{
        if (menuLevel2.ParentCategoryId == ParentId)
        {
                    @menuLevel2.Name
        }
}
}