使用字符串在VB.net中创建Json，并在WebRequest中使用它
使用字符串在VB.net中创建Json，并在WebRequest中使用它
提问于 2020-07-16 09:12:43
我试图在vb.net中调用vb.net，因此试图遵循文件/实例。下面的示例显示了以下代码作为工作示例：
Sub Main(args As String())
Dim request = TryCast(System.Net.WebRequest.Create("https://api.openrouteservice.org/v2/directions/driving-car/gpx"), System.Net.HttpWebRequest)
request.Method = "POST"
request.Accept = "application/json, application/geo+json, application/gpx+xml, img/png; charset=utf-8"
request.Headers.Add("Authorization", "xxxxMYKEYxxxx")
request.Headers.Add("Content-Type", "application/json; charset=utf-8")
Using writer = New System.IO.StreamWriter(request.GetRequestStream())
Dim byteArray As Byte() = System.Text.Encoding.UTF8.GetBytes({"coordinates:[[8.681495,49.41461],[8.686507,49.41943],[8.687872,49.420318]]"})
request.ContentLength = byteArray.Length
writer.Write(byteArray)
writer.Close()
End Using
Dim responseContent As String
Using response = TryCast(request.GetResponse(), System.Net.HttpWebResponse)
Using reader = New System.IO.StreamReader(response.GetResponseStream())
responseContent = reader.ReadToEnd()
Console.WriteLine(responseContent.ToString())
End Using
End Using
End Sub该示例表明，请求主体的内容应该如下：
{"coordinates":[[8.681495,49.41461],[8.686507,49.41943],[8.687872,49.420318]]}但是，在运行该示例时，我会得到以下错误：
'The remote server returned an error: (500) Internal Server Error.'因此，我认为请求失败是因为无效的Json。我的问题是如何创建与上面提供的示例- JSON相同的JSON？
回答 1
Stack Overflow用户
回答已采纳
发布于 2020-07-16 10:05:43
API期望有一个JSON对象，表示一个双值数组，作为HttpRequest的内容，编码为UTF-8字符串，作为字节数组发送。
此集合可以由List(Of List(Of Double)属性类型.Net类表示：
' Note that JavaScriptSrializer might ignore <JsonProperty>,
' so use lower case, since the Web API is case-sensitive
Friend Class MyObject
<JsonProperty("coordinates")>
Public Property coordinates As List(Of List(Of Double))
End Class在此之后，我们只需填写清单：
Dim myobj = New MyObject() With {
.Coordinates = New List(Of List(Of Double)) From {
New List(Of Double)({8.681495, 49.41461}),
New List(Of Double)({8.686507, 49.41943}),
New List(Of Double)({8.687872, 49.420318})
}
}并使用Json.Net (通过NuGet包管理器安装NuGet包)或JavaScriptSerializer (或任何其他可用的JSON序列化程序)对其进行序列化：
JavaScriptSerializer需要对System.Web.Extension的项目引用并导入System.Web.Script.Serialization。
' Using Json.Net
Dim Json As String = JsonConvert.SerializeObject(myobj)
' Or JavaScriptSerializer
Dim json = New JavaScriptSerializer().Serialize(myobj)►原始代码有多个问题：
webRequest.ContentLength设置得太晚了:它需要在发送请求之前设置- 用于写入StreamWriter流的WebRequest将危及进程:不需要它，并且在将字节写入请求流之前它将被关闭
- 不能使用标头设置
WebRequest.ContentType，必须使用Content-Type属性 - 如果在Windows 7或WM中使用此代码，则添加
SecurityProtocolType.Tls12(在Windows 7中，默认为SecurityProtocolType.Ssl3 Or SecurityProtocolType.Tls，因此TLS1.0不再真正使用，此时TLS1.2仍然是主要参与者)
修正了原始代码，使用JavaScriptSerializer序列化请求数据：
如果使用Imports System.Web.Script.Serialization，则用Imports Newtonsoft.Json替换Json.Net。
Imports System.IO
Imports System.Text
Imports System.Web.Script.Serialization
Dim myobj = New MyObject() With {
.Coordinates = New List(Of List(Of Double)) From {
New List(Of Double)({8.681495, 49.41461}),
New List(Of Double)({8.686507, 49.41943}),
New List(Of Double)({8.687872, 49.420318})
}
}
Dim json As String = New JavaScriptSerializer().Serialize(myobj)
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
Dim request = WebRequest.CreateHttp("https://api.openrouteservice.org/v2/directions/driving-car/gpx")
request.Method = "POST"
request.PreAuthenticate = True
request.Accept = "application/json, application/geo+json, application/gpx+xml, img/png; charset=utf-8"
request.Headers.Add("Authorization", "[Your API Key]")
request.ContentType = "application/json; charset=utf-8"
Dim jsonBytes = Encoding.UTF8.GetBytes(json)
request.ContentLength = jsonBytes.Length
Using reqStream = request.GetRequestStream()
reqStream.Write(jsonBytes, 0, jsonBytes.Length)
End Using
Dim responseContent As String = String.Empty
Using response = DirectCast(request.GetResponse(), HttpWebResponse),
responseStream = response.GetResponseStream(),
reader = New StreamReader(responseStream)
responseContent = reader.ReadToEnd()
End Using页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/62931337
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