Below code is working fine on Umbraco 8

  @{

      var newsList = Model.Parent.Children("alias").ToList();
        var currentIndexInNewsList = newsList.FindIndex(x => x.Id.Equals(Model.Id));
       var  totalResults = newsList.Count();

        if (currentIndexInNewsList > -1)
                {

                 if (currentIndexInNewsList > 0)
                    {
                        var previousItem = newsList[currentIndexInNewsList - 1]; 
                        <div class="col-xl-6 col-lg-6 col-sm-12 prevFooter">
                                <a href="@previousItem.Url"><span><i class="fas fa-arrow-left"></i></span>Previous Project</a>
                            </div>

                    }   
                    if (totalResults-1 > currentIndexInNewsList)
                    {
                        var nextItem = newsList[currentIndexInNewsList + 1];
                         <div class="col-xl-6 col-lg-6 col-sm-12 nextFooter">
                            <a href="@nextItem.Url"><span></span>Next Project</a>
                        </div>

                    }


    }

}