通过JArray的NewtonSoft JSON循环 [英] NewtonSoft JSON Loop Through JArray

问题描述

我正在尝试遍历JArray，并且在for/next循环内未将msg声明为错误.

I'm attempting to loop through a JArray and I'm getting msg is not declared error inside my for/next loop.

我的JSON格式如下...

My JSON is formatted like this...

{ "messages":[
      {
        "id": 123456789,
        "sender_id": 1236547890,
        "replied_to_id": null,
        "created_at": "2017/09/28 15:49:20 +0000",
        "network_id": 554477,
        "message_type": "update",
        "sender_type": "user",
        "url": "https://www.example.com",
        "web_url": "https://www.example.com/123456789",
        "group_id": 7418529,
        "body": {
          "urls": [
            "https://www.facebook.com/blah/blah/blah",
            "https://google.com/foo/bar"
          ],
          "parsed": "Sem, imperdiet voluptatibus. Molestias, gravida vehicula, irure suscipit. Dis facilisi laudantium recusandae necessitatibus dolor quaerat quisque! Lectus deserunt taciti magnis, a non eligendi similique? Exercitationem eius corporis. Faucibus eiusmod delectus voluptatum nascetur, alias doloremque sagittis, repellendus laudantium quae, iaculis, cras maecenas fusce suspendisse amet magnam nulla gravida mollis, tempora gravida",
          "plain": "Sem, imperdiet voluptatibus. Molestias, gravida vehicula, irure suscipit. Dis facilisi laudantium recusandae necessitatibus dolor quaerat quisque! Lectus deserunt taciti magnis, a non eligendi similique? Exercitationem eius corporis. Faucibus eiusmod delectus voluptatum nascetur, alias doloremque sagittis, repellendus laudantium quae, iaculis, cras maecenas fusce suspendisse amet magnam nulla gravida mollis, tempora gravida",
          "rich": "Sem, imperdiet voluptatibus. Molestias, gravida vehicula, irure suscipit. Dis facilisi laudantium recusandae necessitatibus dolor quaerat quisque! Lectus deserunt taciti magnis, a non eligendi similique? Exercitationem eius corporis. Faucibus eiusmod delectus voluptatum nascetur, alias doloremque sagittis, repellendus laudantium quae, iaculis, cras maecenas fusce suspendisse amet magnam nulla gravida mollis, tempora gravida"
        },
        "thread_id": 956818730,
        "client_type": "Zapier",
        "client_url": "https://zapier.com/zapbook/example/",
        "system_message": false,
        "direct_message": false,
        "chat_client_sequence": null,
        "language": "en",
        "notified_user_ids": [],
        "privacy": "public",
        "attachments": [],
        "liked_by": {
          "count": 0,
          "names": []
        },
        "content_excerpt": "Sem, imperdiet voluptatibus. Molestias, gravida vehicula, irure suscipit. Dis facilisi laudantium recusandae necessitatibus dolor quaerat quisque! Lectus deserunt taciti magnis, a non eligendi similique? Exercitationem eius corporis. Faucibus eiusmod delectus voluptatum nascetur, alias doloremque sagittis, repellendus laudantium quae, iaculis, cras maecenas fusce suspendisse amet magnam nulla gravida mollis, tempora gravida",
        "group_created_id": 7418529
      },
      {
        "id": 987654321,
        "sender_id": 3214569870,
        "replied_to_id": 123555777,
        "created_at": "2017/09/28 15:28:28 +0000",
        "network_id": 554477,
        "message_type": "update",
        "sender_type": "user",
        "url": "https://www.example.com",
        "web_url": "https://www.example.com/987654321",
        "body": {
          "parsed": "Veniam quasi sem, neque netus? Eos quae voluptatibus autem optio varius euismod voluptas, voluptatum inventore",
          "plain": "Veniam quasi sem, neque netus? Eos quae voluptatibus autem optio varius euismod voluptas, voluptatum inventore",
          "rich": "Veniam quasi sem, neque netus? Eos quae voluptatibus autem optio varius euismod voluptas, voluptatum inventore"
        },
        "thread_id": 956224600,
        "client_type": "Web",
        "client_url": "https://www.example.com/",
        "system_message": false,
        "direct_message": false,
        "chat_client_sequence": null,
        "language": "en",
        "notified_user_ids": [],
        "privacy": "public",
        "attachments": [],
        "liked_by": {
          "count": 0,
          "names": []
        },
        "content_excerpt": "Veniam quasi sem, neque netus? Eos quae voluptatibus autem optio varius euismod voluptas, voluptatum inventore",
        "group_created_id": null
      }
    ]}

这是我试图用来遍历JArray的代码...

Here's the code I'm attempting to use to loop through the JArray...

Dim jObj As JObject = JObject.Parse(File.ReadAllText(outputJSONpath & "myFile.json"))
Dim jArr As JArray = CType(jObj("messages"), JArray)
Dim i As Int32 = 0
For Each msg As JObject In jArr 
    Dim threadID = msg.GetValue("thread_ID")
    'Do Work
Next

当我执行jArr.Count时，它将返回6,341.为什么没有声明味精?如何获取我的6,341消息中的每一个的thread_ID值?

When I do a jArr.Count it returns 6,341. Why is msg not declared? How do I get to the value for thread_ID for each of my 6,341 msg?

推荐答案

我不确定您对未声明msg的意思-最肯定是在您的For Each循环中声明了它.听起来好像数组中的一个或多个消息项实际上可能是null或不是JObject.在尝试使用JToken之前，您可能需要进行一些防御性的编码，并检查是否为null，以及是否得到的JToken类型是否符合您的期望.与thread_ID值类似.也许是这样的:

I'm not sure what you mean about msg not being declared-- it is most definitely declared right there in your For Each loop. It sounds like maybe one or more of the message items inside the array might actually be null or not a JObject. You might need to code a little more defensively and check for null and also whether the type of JToken you are getting is what you expect before trying to use it. Similarly with the thread_ID value. Perhaps something like this instead:

For Each msg As JToken In jArr

    If Not msg Is Nothing AndAlso msg.Type = JTokenType.Object Then

        Dim threadID As JToken = msg("thread_ID")
        If Not threadID Is Nothing AndAlso threadID.Type = JTokenType.Integer Then

            Dim id As Integer = CType(threadID, Integer)

            '... Do something with id
            Console.WriteLine(id)

        End If

    End If

Next

更新

好的，我知道问题出在哪里.在JToken上使用GetValue()或索引器语法(即msg("thread_ID"))时，属性名称区分大小写.在您的代码中，您有thread_ID，但是在JSON中是thread_id，因此代码永远找不到它.

OK, I see what the issue is now. When you use GetValue() or the indexer syntax, i.e. msg("thread_ID"), on a JToken, the property name is case sensitive. In your code, you have thread_ID, but in the JSON it is thread_id, so the code never finds it.

更改:

Dim threadID As JToken = msg("thread_ID")

收件人:

Dim threadID As JToken = msg("thread_id")

它应该可以工作.

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