Question

对C＃来说还是个新手，非常感谢任何帮助。

获得以下错误： “你调用的对象是空的。”当我尝试访问recipeinforeturned.resultslist [0] .title或列表中的任何其他元素时。

然而，我能够成功返回recipereturned.title。

这是带有json格式的api URL：

http://www.recipepuppy.com/api/?i=onions,garlic&q=omelet&p=3

    protected void getButton_Click(object sender, EventArgs e)
    {
        string url = string.Format("http://www.recipepuppy.com/api/?i={0}&q={1}", ingredientsTextBox.Text, recipetypeTextBox.Text);

        using (WebClient client = new WebClient())
        {
            string json = client.DownloadString(url);
            RecipeInfo recipeinforeturned = new RecipeInfo();
            recipeinforeturned = (new JavaScriptSerializer()).Deserialize <RecipeInfo>(json);
            //next need a loop to go through each list item and add to ResultsListBox to end of recipies
            Label1.Text = recipeinforeturned.title;
            for (int i = 0; i < recipeinforeturned.resultslist.Count; i++)

            {
               resultsListBox.Items.Add(recipeinforeturned.resultslist[i].title);
                resultsListBox.Items.Add(recipeinforeturned.resultslist[i].ingredients);
                resultsListBox.Items.Add(Environment.NewLine);
            }
        }


    }

    public class RecipeInfo
    {      
        public string title { get; set; }
        public string version { get; set; }
        public string href { get; set; }
        public List<Results> resultslist { get; set; }
    }

    public class Results

    {
        public string title { get; set; }
        public string href { get; set; }
        public string ingredients { get; set; }
        public string thumbnail { get; set; }
    }
}

} 任何帮助将不胜感激。

Answer 1

您可以尝试将“Version”字符串的字段类型更改为double。

 public class RootObject
{
    public string title { get; set; }
    public double version { get; set; }
    public string href { get; set; }
    public List<Result> results { get; set; }
}

Answer 2

您需要重命名：

public List<Results> resultslist { get; set; }

到

public List<Results> results { get; set; }

否则反序列化器会在您的JSON中查找resultslist对象，但无法找到它，因此会返回null

json的反序列化在格式正确的json中返回null

2 个答案: