问题描述
我需要从YouTube上获得的响应中获取标题".我在第8行的位置12，即在行上得到以下错误:
I need to obtain the "title" from the response i get from Youtube.I get the following error at line 8, position 12, that is, at line:
"items": [
紧接在"["
我得到的错误是:
Exception: Exception thrown: 'Newtonsoft.Json.JsonSerializationException' in Newtonsoft.Json.dll ("Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'categoryid.Item' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.
To fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List<T> that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array.
Path 'items', line 8, position 12."). Exception thrown: 'Newtonsoft.Json.JsonSerializationException' in Newtonsoft.Json.dll ("Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'categoryid.Item' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.
To fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List<T> that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array.
Path 'items', line 8, position 12.") 2.61s [12096] <No Name>
我有此代码:
Dim m As IEnumerable(Of Rootobject) = JsonConvert.DeserializeObject(Of IEnumerable(Of Rootobject))(res)
具有以下JSON数据:
with this JSON data:
{
"kind":"youtube#videoListResponse",
"etag":"\"m2yskBQFythfE4irbTIeOgYYfBU/jznkhy3_Aws9VtommTkcdOYnAAk\"",
"pageInfo":{
"totalResults":1,
"resultsPerPage":1
},
"items":[
{
"kind":"youtube#video",
"etag":"\"m2yskBQFythfE4irbTIeOgYYfBU/M_wQmC4lQBaHJGxo79N7WlmqNr8\"",
"id":"SSbBvKaM6sk",
"snippet":{
"publishedAt":"2009-04-15T20:31:11.000Z",
"channelId":"UC2kTZB_yeYgdAg4wP2tEryA",
"title":"Blur - Song 2",
"description":"Blur 21 -- Celebrating 21 years of Blur. To find out more, click here:http://smarturl.it/blur21y\n\n#blur21\n \nFollow Blur on Twitter:www.twitter.com/blurofficial \nFind Blur on Facebook:www.facebook.com/blur\n\nMusic video by Blur performing Song 2.",
"thumbnails":{
"default":{
"url":"https://i.ytimg.com/vi/SSbBvKaM6sk/default.jpg",
"width":120,
"height":90
},
"medium":{
"url":"https://i.ytimg.com/vi/SSbBvKaM6sk/mqdefault.jpg",
"width":320,
"height":180
},
"high":{
"url":"https://i.ytimg.com/vi/SSbBvKaM6sk/hqdefault.jpg",
"width":480,
"height":360
},
"standard":{
"url":"https://i.ytimg.com/vi/SSbBvKaM6sk/sddefault.jpg",
"width":640,
"height":480
},
"maxres":{
"url":"https://i.ytimg.com/vi/SSbBvKaM6sk/maxresdefault.jpg",
"width":1280,
"height":720
}
},
"channelTitle":"emimusic",
"tags":[
"Blur",
"Song"
],
"categoryId":"10",
"liveBroadcastContent":"none",
"localized":{
"title":"Blur - Song 2",
"description":"Blur 21 -- Celebrating 21 years of Blur. To find out more, click here:http://smarturl.it/blur21y\n\n#blur21\n \nFollow Blur on Twitter:www.twitter.com/blurofficial \nFind Blur on Facebook:www.facebook.com/blur\n\nMusic video by Blur performing Song 2."
}
},
"contentDetails":{
"duration":"PT2M3S",
"dimension":"2d",
"definition":"sd",
"caption":"false",
"licensedContent":true,
"regionRestriction":{
"allowed":[
"BY",
"US"
]
},
"projection":"rectangular"
}
}
]
}
和这些类. Visual Studio 2015选项将这些课程粘贴为特殊课程.
and these classes. the classes are pasted as special with the visual studio 2015 option.
Public Class Rootobject
Public Property kind As String
Public Property etag As String
Public Property pageInfo As Pageinfo
Public Property items() As Item
End Class
Public Class Pageinfo
Public Property totalResults As Integer
Public Property resultsPerPage As Integer
End Class
Public Class Item
Public Property kind As String
Public Property etag As String
Public Property id As String
Public Property snippet As Snippet
Public Property contentDetails As Contentdetails
End Class
Public Class Snippet
Public Property publishedAt As Date
Public Property channelId As String
Public Property title As String
Public Property description As String
Public Property thumbnails As Thumbnails
Public Property channelTitle As String
Public Property tags() As String
Public Property categoryId As String
Public Property liveBroadcastContent As String
Public Property localized As Localized
End Class
Public Class Thumbnails
Public Property _default As _Default
Public Property medium As Medium
Public Property high As High
Public Property standard As Standard
Public Property maxres As Maxres
End Class
Public Class _Default
Public Property url As String
Public Property width As Integer
Public Property height As Integer
End Class
Public Class Medium
Public Property url As String
Public Property width As Integer
Public Property height As Integer
End Class
Public Class High
Public Property url As String
Public Property width As Integer
Public Property height As Integer
End Class
Public Class Standard
Public Property url As String
Public Property width As Integer
Public Property height As Integer
End Class
Public Class Maxres
Public Property url As String
Public Property width As Integer
Public Property height As Integer
End Class
Public Class Localized
Public Property title As String
Public Property description As String
End Class
Public Class Contentdetails
Public Property duration As String
Public Property dimension As String
Public Property definition As String
Public Property caption As String
Public Property licensedContent As Boolean
Public Property regionRestriction As Regionrestriction
Public Property projection As String
End Class
Public Class Regionrestriction
Public Property allowed() As String
End Class
我需要做什么?预先感谢.
What i need to do?Thanks in advance.
推荐答案
您将收到该异常，因为您错误地声明了几个自动实现的数组属性.如 自动实现的属性(Visual Basic) 此类属性应声明如下，并且()数组指示符应作为返回类型的一部分:
You are getting that exception because you have declared several auto-implemented array properties incorrectly. As shown in Auto-Implemented Properties (Visual Basic) such properties should be declared as follows, with the () array indicator as part of the return type:
Public Property items As Item()
相反，您可以如下声明它们:
Instead you declare them as follows:
Public Property items() As Item
这声明了一个属性，该属性返回单个Item而不是它们的数组.附在属性名称上的()是可选的；对于无参数属性，这是多余的，但是对于采用参数的属性，参数列表将显示在此处.请参阅文档页面 属性声明 以获取详细信息.然后，Json.NET会在尝试将JSON数组反序列化为模型中的非数组属性之一时引发您看到的异常.
This declares a property returning a single Item rather than an array of them. The () attached to the property name is optional; for parameterless properties it is redundant but for properties taking parameters the argument list appears there. See the documentation page Property Statement for details. Then Json.NET throws the exception you see when attempting to deserialize a JSON array into one of the non-array properties in your model.
要解决此问题，应按如下所示修改您的三个类:
To fix this, three of your classes should be modified as follows:
Public Class Rootobject
Public Property kind As String
Public Property etag As String
Public Property pageInfo As Pageinfo
Public Property items As Item() ' Fixed
End Class
Public Class Snippet
Public Property publishedAt As Date
Public Property channelId As String
Public Property title As String
Public Property description As String
Public Property thumbnails As Thumbnails
Public Property channelTitle As String
Public Property tags As String() ' Fixed
Public Property categoryId As String
Public Property liveBroadcastContent As String
Public Property localized As Localized
End Class
Public Class Regionrestriction
Public Property allowed As String() ' Fixed
End Class
然后，由于items是一个数组，因此可以访问标题并将其放在列表中，因此可以使用 System.Linq.Enumerable :
Then, since the items are an array, to access the titles and put then in a list, you can use extension methods from System.Linq.Enumerable:
' Convert the json string to RootObject.
Dim root = JsonConvert.DeserializeObject(Of Rootobject)(json)
' Extract the list of titles.
Dim titles = root.items _
.Select(Function(i) i.snippet.title) _
.ToList()
' Get the first title in the list.
Dim firstTitle = titles.FirstOrDefault()
Console.WriteLine("First title = ""{0}""", firstTitle)
哪个打印出First title = "Blur - Song 2".
示例 VB.Net小提琴.
这篇关于Json无法使用VB.net反序列化YouTube数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！