Remotely/Server/Components/TabControl/TabHeader.razor

<li class="nav-item">
    <a class="nav-link @ActiveClass" data-toggle="tab" @onclick="SetActiveTab" style="cursor: pointer; user-select: none;">
        @ChildContent
    </a>
</li>

@code {
    [CascadingParameter]
    public TabControl Parent { get; set; }

    [Parameter]
    public RenderFragment ChildContent { get; set; }

    [Parameter]
    public Action OnActivated { get; set; }

    [Parameter]
    public string Name { get; set; }

    private string ActiveClass => Parent.ActiveTab == Name ? "active" : "";

    protected override void OnInitialized()
    {
        if (Parent is null)
        {
            throw new Exception("TabHeader must be contained in a TabControl.");
        }
        base.OnInitialized();
    }

    private void SetActiveTab()
    {
        Parent.SetActiveTab(this);
        StateHasChanged();
        OnActivated?.Invoke();
    }
}