“System.NullReferenceException”类型的未处理异常

Question

这是我的代码：

var reddit = new Reddit();
var authenticated = false;
try
{
    var user = reddit.LogIn("uname", "password");
    authenticated = reddit.User != null;
}
catch (AuthenticationException)
{
    Console.WriteLine("Incorrect login.");
    authenticated = false;
}
//RedditSharp.Things.Thing.Parse.
var subreddit = reddit.RSlashAll;
var allPost = subreddit.Search("domain").Take(3);
foreach(var p in allPost)
{
    Console.WriteLine(p.Comments);
    var comment = p.Comment("aaaaaaaaaaaaaaaaaa");
    comment.Distinguish(RedditSharp.Things.VotableThing.DistinguishType.Moderator);
}

我收到类型

的未处理异常

  

RedditSharp.dll中出现未处理的“System.NullReferenceException”类型异常   附加信息：对象引用未设置为的实例   对象

发生在

var comment = p.Comment("aaaaaaaaaaaaaaaaaa");

Answer 1

错误消息引用了错误的行。在询问值之前检查p.comments是否为空。

foreach(var p in allPost)
{
  if(p.comments != null)
  {
    Console.WriteLine(p.Comments);
    var comment = p.Comment("aaaaaaaaaaaaaaaaaa");
  }    
}