Blazor treeview

RecursiveUI.razor

@inject NavigationManager _navigated

@foreach (var category in categories.Where(subcatg => subcatg.CategoryParentId == ParentId))
{
    bool isCollapse     = true;
    string node         = category.CategoryName;
    bool hasSubcategory = categories.Where(subcatg => subcatg.CategoryParentId == category.CategoryId).Any()
    bool canExpand      = isCollapse == @isCollapseNavMenu && node == @nodeParent && hasSubcategory

    <li class="nav-item px-2">
        <NavLink @onclick="@(() => ToggleNavMenu(category))" class="nav-link">@category.CategoryName.Split(";")[0]</NavLink>
        @if (canExpand)
        {
            <ul class="nav flex-column">
                <RecursiveUI ParentId="category.CategoryId"></RecursiveUI>
            </ul>
        }
    </li>
}

@code {
    [Parameter]
    public int ParentId { get; set; }

    [CascadingParameter]
    public List<Category> categories { get; set; }

    private bool isCollapseNavMenu = false;
    private String nodeParent = null;

    private void ToggleNavMenu(Category category)
    {
        isCollapseNavMenu = !isCollapseNavMenu;
        this.nodeParent = category.CategoryName;
        StateHasChanged();
        this._navigated.NavigateTo($@"/Shop/Products/{category.CategoryName.Split(";")[1]}");
    }
}

Treeview.razor

@inject IRestService _restService
@inject NavigationManager _navigated

<CascadingValue Value="categories">
    <ul class="nav flex-column">
        <RecursiveUI ParentId=0></RecursiveUI>
    </ul>
</CascadingValue>

@code {
    List<Category> categories = new List<Category>();

    protected override async Task OnInitializedAsync()
    {
        try
        {
            this.categories = await this._restService.GetCategories();                       
        }
        catch (Exception)
        {
            this._navigated.NavigateTo("/");
        }
    }
}