Added support for rendering IEnumerable entities

[AbdoMahfoz]

Consider the following case

public class Category : BaseModel
{
    [Required] public string Name { get; set; }

    public int? ParentId { get; set; }
    public virtual Category Parent { get; set; }
    
    public virtual ICollection<Category> Children { get; set; }
    public virtual ICollection<Product> Products { get; set; }

    public override string ToString() => $"{Name} - {(ParentId == null ? "root" : "child")}";
}

Currently, navigation properties Children and Products cause the code to crash.
After inspecting the code I found that there is no support for rendering such properties.
So, I made the controller eager load the entities before sending them to the View to avoid the crash, then I added code in the view that should render these properties as <ul>

[rezabashiri]

strings behave like value variables and each time you add to them create another variable and its not optimum, better to use stringbuilder

[Plotron]

What's up with that? Consuming exceptions like that is an anti-pattern. Shouldn't there be a way to avoid an NRE in the first place?