Referenced Blazor component is null

Consider the following Blazor code:

<Foo @ref="foo"><Bar @ref="bar"/></Foo><button @onclick="() => LoadBar("some data")">Click</button>@code {    private Bar bar = null!;    private void LoadBar(string data)    {        bar.SetData(data) // bar is null        foo.SetVisible(true); // foo is not null, but exception already thrown    }}

When I click the button, I want it to call LoadBar and pass some data to the referenced Bar instance, but the instance is always null. I'm not sure why, although it may be to do with the way it's rendered by Foo; i.e. if isVisible is false in Foo, then Bar will not be rendered.

What sort of approaches does Blazor provide for this scenario?