Check if SharePoint List already Exists using ClientContext

 private bool ValdiateList(ClientContext clientContext, string listName, out List existingList)
        {

            Web web = clientContext.Web;

            existingList = null;

            ListCollection lists = web.Lists;

            IEnumerable<List> existingLists = clientContext.LoadQuery(lists.Where(list => list.Title == listName));

            clientContext.ExecuteQuery();

            existingList = existingLists.FirstOrDefault();

            if (existingList != null)

                return true;

            else

                return false;

        }