Blazor server - Fluent UI - Set focus to a FluentDatePicker

I can set focus to a FluentTextField:

• Use a @ref: @ref=myFluentTextField

• Declare it as a FluentTextField:FluentTextField? nombreFluentTextField;

• Set focus:

  protected override void OnAfterRender(bool firstRender) { nombreFluentTextField?.FocusAsync(); }

If I try to do the same with a FluentDatePicker, I get this error in the console:

ElementReference has not been configured correctly.

So, the question is: how to set focus from code to a FluentDatePicker?

Many thanks and bye ...