private void SetCompletionDisplaySide() { var popupMargin = new Thickness(0); suggestionPopupDisplaySide = this.GetDisplaySide(); switch (suggestionPopupDisplaySide) { case SuggestionPopupDisplaySide.Top: var autoCompleteHeight = this.CalculateAutoCompleteListBoxHeight(); popupMargin.Top = -autoCompleteHeight; break; case SuggestionPopupDisplaySide.Bottom: popupMargin.Top = this.textBox.ActualHeight; break; } this.autoCompletePresenter.Margin = popupMargin; }