How to add childcomponent to mudstack in my code

 private RenderFragment RenderSimpleElement() => builder =>    {        int seq = 0;        builder.OpenComponent<MudStack>(seq++);        builder.AddAttribute(seq++,"Child","");        builder.OpenComponent<StoragePlace>(seq++);        builder.AddAttribute(seq++, "Name", "kukuku");        builder.AddAttribute(seq++, "Width", "180px");        builder.AddAttribute(seq++, "Height", "260px");        builder.CloseComponent();        builder.OpenComponent<StoragePlace>(seq++);        builder.AddAttribute(seq++, "Name", "hahaha");        builder.AddAttribute(seq++, "Width", "180px");        builder.AddAttribute(seq++, "Height", "260px");        builder.CloseComponent();        builder.CloseComponent();    };

this cant work!I can compile it, but when rendering this interface, the following error occurs. I think it might not be possible to add child components to the mud stack like this：

System.AggregateException: One or more errors occurred. (Error: No element is currently associated with component 78) ---> System.InvalidOperationException: Error: No element is currently associated with component 78

so what is the correct method?i need to add childcomponent to mudstack this way.