C# Html Agility Pack'；s LoadFromWebAsync

我正在使用Html Agility Pack从URL获取元标记。我使用的是

HtmlWeb

的

Load

，但我发现它花费的时间太长，我认为我可以使用异步方法来提高性能。然而，当我尝试使用

LoadFromWebAsync

时，我得到了一个NullReferenceException

使用

Load

公共静态元标记GetMetaData（字符串url）
{
//这很有效
var webGet=new HtmlWeb（）；
var document=webGet.Load（url）；
var metaTags=document.DocumentNode.SelectNodes（“//meta”）；
MetaTags metaInfo=新的MetaTags（url）；
//更多代码
}

使用

LoadFromWebAsync

公共静态异步任务GetMetaData（字符串url） { //这不管用 var webGet=new HtmlWeb（）； var document=wait webGet.LoadFromWebAsync（url）；//在此处中断 var metaTags=document.DocumentNode.SelectNodes（“//meta”）； MetaTags metaInfo=新的MetaTags（url）； //更多代码 } 我使用此方法获取要传递到

新闻卡

组件的url数据，我尝试这样做：

---

问题是我试图在加载数据之前显示数据。这是因为我在使用async，但在它等待结果时没有提供要显示的内容。可以通过执行以下操作进行修复：

if（news.HasData==false）{
装载

}
否则{

@新闻，标题

}
@代码{
公共元标记新闻{get；set；}
受保护的重写异步任务OnInitializedAsync（）
{
news=newmetatags（newsUrl）；//初始化为HasData=false
news=wait MetaScraper.GetMetaData（newsUrl）；//稍后填写数据。
}
}
到底是什么东西坏了？在本例中，什么是null？我尝试了异步方法，它可以正常工作到这一行：var metaTags=document.DocumentNode.SelectNodes（“//meta”）；//它包含一个HtmlNodeCollection，您可以进一步处理它。我不确定什么是空的，我在Blazor中工作，当它中断时，它会退出到_Host.cshtml的这一行：
服务器预渲染
用于Blazor服务器，这意味着您可以调试应用程序并使用断点。您还可以使用异常处理和日志记录来查看引发异常的位置。完整的异常文本包含引发异常的位置，以及显示导致异常的调用的堆栈跟踪it@PanagiotisKanavos我已经更新了我的问题，以包括堆栈跟踪，但我对它的理解还不够透彻，无法将其指向导致问题的一行代码。在
等待…
行之后，我无法点击任何断点。请接受您的答案，以便问题可以显示为答案。我不能，您必须等待24小时才能接受您发布到您自己问题上的答案
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