ds-select.component.html

<div>

  <div ngbDropdown class="btn-group" (openChange)="toggled.emit($event)">

    <div class="input-group-prepend" *ngIf="label">
      <span id="dsSelectMenuLabel-{{ uniqueId }}" class="input-group-text">
        {{ label | translate }}
      </span>
    </div>

    <button [attr.aria-describedby]="label ? 'dsSelectMenuLabel-' + uniqueId : null"
            id="dsSelectMenuButton-{{ uniqueId }}"
            class="btn btn-outline-primary selection"
            (blur)="close.emit($event)"
            (click)="close.emit($event)"
            [dsBtnDisabled]="disabled"
            ngbDropdownToggle>
      <ng-content select=".selection"></ng-content>
    </button>

    <div ngbDropdownMenu
         class="dropdown-menu"
         id="dsSelectDropdownMenu-{{ uniqueId }}"
         [attr.aria-labelledby]="'dsSelectMenuButton-' + uniqueId">
      <div>
        <ng-content select=".menu"></ng-content>
      </div>
    </div>
  </div>

</div>