在连接到字符串时处理LINQ中的空列

contactTable.Select(c => c.Title + \" \" + c.FirstName).ToList();

contactTable.Select(c => (string.IsNullOrEmpty(c.Title) ? \"\" : c.Title + \" \") + c.FirstName).ToList();

contactDetails = contactTable.Select(c =>
            ((c.Title ?? \"\") + \" \" + c.FirstName).Trim() + \" \" + ((c.MiddleName ?? \"\") + \" \" + c.LastName).Trim()).ToList();

contactTable.Select(c => ( (( c.Title ?? \"\") + \" \"  + c.FirstName).Trim()).ToList();