Question

我有这个代码，它从Api链接中检索Json值并将它们输入到列表中。在此列表中有ID，如果存在于另一个API链接中，则会检查所有这些ID。

private void button1_Click(object sender, EventArgs e)
{   
    var spidyApi_searchIdByName_result = api_Handler.GetApi(spidyApi_searchIdByName);
    var Gw2Api_isItemIdinListing_result = api_Handler.GetApi(Gw2Api_allListings + spidyApi_searchIdByName_result.???); // can't access object property      
}

这是GetApi方法：

public object GetApi(string url)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);

    try
    {
        WebResponse response = request.GetResponse();
        using (Stream responseStream = response.GetResponseStream())
        {
            StreamReader reader = new StreamReader(responseStream, Encoding.UTF8);
            var jsonReader = new JsonTextReader(reader);
            var serializer = new JsonSerializer();
            return serializer.Deserialize<RootObject>(jsonReader);
        }
    }

    catch (WebException)
    {       
        return Newtonsoft.Json.JsonConvert.DeserializeObject<A>("{\"text\":\"no such id\"}");
    }

}

这是GetApi()方法反序列化的RootObject：

public class RootObject
{
    public int id { get; set; }
    // ...
}

但是，从object返回GetApi()时，我无法访问返回的对象的属性。我怎样才能访问这些？

Answer 1

你有两个问题。

首先，您从方法中返回object，因此无法访问any members that object doesn't have。这就是为什么你应该返回一个更专业的类型like I already advised，所以在这种情况下：

public RootObject GetApi(string url)
{
    // ...
    return serializer.Deserialize<RootObject>(jsonReader);
}

但是，您希望此方法能够执行更多操作。您希望从中返回两种类型，并添加错误处理。

泛型（参见T）可以在这里提供帮助，您可以在调用方法时指定类型：

public T GetObjectFromApi<T>(string url)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);

    try
    {
        WebResponse response = request.GetResponse();
        using (Stream responseStream = response.GetResponseStream())
        {
            StreamReader reader = new StreamReader(responseStream, Encoding.UTF8);
            var jsonReader = new JsonTextReader(reader);
            var serializer = new JsonSerializer();
            return serializer.Deserialize<T>(jsonReader);
        }
    }
    catch (WebException)
    {       
        return null;
    }
}

然后这样称呼：

var spidyApi_searchIdByName_result = api_Handler.GetObjectFromApi<spidyApiResult>(spidyApi_searchIdByName);
if (spidyApi_searchIdByName_result != null)
{
    var Gw2Api_isItemIdinListing_result = api_Handler.GetApi<RootObject>(Gw2Api_allListings + spidyApi_searchIdByName_result.someProperty);
}

当然这会吞下WebException。

返回对象时无法访问自定义类属性

1 个答案: