Question

我正在使用JSON对象从各种网站获取新闻标题。当我解压缩它时，我可以访问一个标题但是当我尝试循环这些项目并将它们添加到列表中以获取所有标题时，我收到以下错误：

'System.Collections.Generic.List.Add（string）'的最佳重载方法匹配有一些无效的参数

我正在使用newtonsoft.json，然后将其变为动态对象，以便通过点表示法进行访问。

JSON示例

{
    "status": "ok",
    "totalResults": 10,
    "articles": [{
        "source": {
            "id": "bloomberg",
            "name": "Bloomberg"
        },
        "author": null,
        "title": "Here’s Where the GOP Tax Plan Stands Right Now",
        "description": "The House is scheduled to vote Tuesday on the tax bill and Senate leaders intend to bring the measure up as soon as they get it.",
        "url": "http://www.bloomberg.com/news/articles/2017-12-19/house-plans-early-vote-democrats-plan-drama-tax-debate-update",
        "urlToImage": "https://assets.bwbx.io/images/users/iqjWHBFdfxIU/isN9fqUqLwpE/v0/1200x800.jpg",
        "publishedAt": "2017-12-19T09:00:00Z"
    }, {
        "source": {
            "id": "bloomberg",
            "name": "Bloomberg"
        },
        "author": "Dana Hull, Sarah Frier",
        "title": "Elon Musk Appears to Have Misfired Direct Message to Oculus CTO",
        "description": "Elon Musk appears to have just given his 16.7 million Twitter followers what he meant to send to the co-founder of the virtual-reality company Oculus: his phone number.",
        "url": "http://www.bloomberg.com/news/articles/2017-12-19/elon-musk-appears-to-have-misfired-direct-message-to-oculus-cto",
        "urlToImage": "https://assets.bwbx.io/images/users/iqjWHBFdfxIU/iqJHjveOq1j8/v1/1200x740.jpg",
        "publishedAt": "2017-12-19T21:41:36Z"
    }]
}

代码：

// Set base Website
var url = "https://newsapi.org/v2/top-headlines?sources=";
// Initiate Client
System.Net.WebClient client = new System.Net.WebClient();
// Get JSON Data
var json = client.DownloadString(url + site + apiKey);
// Convert to dynamic object
dynamic jOutput = JsonConvert.DeserializeObject(json);
// Get Articles
var articles = jOutput.articles;
//Declare List
List<String> titles = new List<String>();
foreach (var article in articles)
 {
   var  articleTitle = article.title;
   titles.Add(articleTitle);       
 }

string title = jOutput.articles[0].title;
//string txt = items[0].title;

Answer 1

当您反序列化为对象或动态类型时，Newtonsoft实际上会为您提供JValue个项目。

所以，这一行：

var articleTitle = article.title;

articleType的类型为JValue，而不是string。因此，当您致电List<string>.Add(articleType)时，它会失败，因为没有超载接受JValue。

幸运的是，JValue重载了强制转换操作符，允许您解包实际值。只需将上述行更改为：

string articleTitle = article.title;

足以使您的代码正常工作。

从嵌套的JSON中检索字符串 - System.Collections.Generic.List`1 [System.String]

1 个答案: