If I try to set the current selected value of a dropdown field, nothing happens

I tried it different ways:

  $members = Member::get()->map()->toArray();
  DropdownField('Test', 'Test', $members, Member::currentUserID());
  DropdownField('Test', 'Test', $members)->setValue(Member::currentUserID());
  DropdownField('Test', 'Test', $members)->setValue(1);

None of these lines above seem to work.
If I call in DropdownField::construct()

  Debug::dump($this->value);

The correct value is returned. But if I insert the same line of code in DropdownField::Field() I get an empty value back.

Am I missing something or is this just not the way it should work?

The form value may be overridden later in the process using setValue(), loadDataFrom()

OK, found the problem:

If I create the Field like this (the name of the field must have "[]" at the end):

DropdownField::create('Test[]', 'Testfield', Member::get()->map('ID', 'Title')->toArray(), 3)->setHasEmptyDefault(true)

I get (as expected) this:

<select name="Test[]" class="chosendropdown chosen" id="BootstrapForm_EditForm_Test">
	<option value=""></option>
	<option value="2">User 2</option>
	<option value="4">User 4</option>
	<option value="3" selected="selected">User 3</option>
	<option value="1">User 1</option>
</select>

But it's somehow strange that i have to add the braces by myself...