Question

我正在从服务中检索Json数据，之后尝试执行此操作，但抛出此异常。有了这个细节附加信息：无法将类型为'System.Object'的对象强制转换为'System.Collections.Generic.List`1 [Sample.Reply]'。有谁知道出了什么问题。

private List<Reply> CreateListFromJson(Stream stream)
    {
        var ser = new DataContractJsonSerializer(typeof(List<Reply>));
        var replies = (List<Reply>)ser.ReadObject(stream);
        return replies;
    }

回复类定义为此

public class Reply
{
    public string comment { get; set; }
    public string username { get; set; }
    public string profile_pic { get; set; }
}

这就是Json的样子

{
"status": "OK",
"Error": "None",
"Reason": "successful",
"details": {
    "replies": [
        {
            "comment": "great",
            "username": "Crimson Kajes",
            "profile_pic": "http://ibotv.iboapis.com/profile/20130506_044930.jpg"
        },
        {
            "comment": "great",
            "username": "Crimson Kajes",
            "profile_pic": "http://ibotv.iboapis.com/profile/20130506_044930.jpg"
        },
        {
            "comment": "wonderful",
            "username": "Crimson Kajes",
            "profile_pic": "http://ibotv.iboapis.com/profile/20130506_044930.jpg"
        },
        {
            "comment": "wow",
            "username": "Crimson Kajes",
            "profile_pic": "http://ibotv.iboapis.com/profile/20130506_044930.jpg"
        },
        {
            "comment": "thank God",
            "username": "Crimson Kajes",
            "profile_pic": "http://ibotv.iboapis.com/profile/20130506_044930.jpg"
        }
    ],
    "totalreply": "5"
}

}

Answer 1

如您所见，您的Reply类仅代表回复属性中的对象。你的模型应该是这样的：

public class Reply
{
    public string comment { get; set; }
    public string username { get; set; }
    public string profile_pic { get; set; }
}

public class Details
{
    public List<Reply> replies { get; set; }
    public string totalreply { get; set; }
}

public class RootObject
{
    public string status { get; set; }
    public string Error { get; set; }
    public string Reason { get; set; }
    public Details details { get; set; }
}

现在你可以使用

var ser = new DataContractJsonSerializer(typeof(RootObject));
var root = (RootObject)ser.ReadObject(stream);

转换为List＆lt;＆gt;时类型System.InvalidCastException的异常

1 个答案: