VB.NET ~ PUT WebRequest 在尝试 GetResponse 时引发异常

Question

我遇到两个例外。第一个在常规代码中，第二个在异常处理块中。

我有这个函数（如下），应该使用 PUT 方法更改 Web API 中的用户设置。一切都运行良好，直到我尝试从网络请求获取响应。然后它引发第一个异常（未知），当我尝试处理错误时，我得到第二个异常“对象引用未设置为对象的实例”。

据我所知，通常会导致此错误的是尝试获取未分配的 Web 请求的响应，但在这种情况下，它已分配且 Uri 有效。所有授权凭据也都是正确的。

这是我的代码：

Try
    Dim webRequest As System.Net.HttpWebRequest
    webRequest = System.Net.HttpWebRequest.Create(InternalSettings.APIurl + "/config")
    webRequest.Headers("Authorization") = InternalSettings.APIpwd
    webRequest.Headers("API-Application-Key") = InternalSettings.APIkey

    webRequest.Method = "PUT"
    webRequest.ContentType = "application/x-www-form-urlencoded"

    Dim postData As String = ""
    postData += "SaveAllCustomersData=false"

    Dim byteArray As Byte() = Encoding.UTF8.GetBytes(postData)

    Dim dataStream As Stream = webRequest.GetRequestStream()
    dataStream.Write(byteArray, 0, byteArray.Length)
    dataStream.Close()

    'The next line will raise an unknown exception
    Dim myHttpWebResponse As HttpWebResponse = webRequest.GetResponse
    Dim responseReader As StreamReader = New StreamReader(myHttpWebResponse.GetResponseStream())
    Dim responseData As String = responseReader.ReadToEnd()

    responseReader.Close()
    webRequest.GetResponse().Close()

Catch ex As WebException
    'The next line will raise a "Object reference not set to an instance of an object" exception
    Dim resp = New StreamReader(ex.Response.GetResponseStream()).ReadToEnd()
    Dim obj = JsonConvert.DeserializeObject(resp)
    Return False
End Try

Answer 1

如果您使用基本身份验证，您可以尝试如下操作：

Dim strUrl As String = InternalSettings.APIurl + "/config"
Dim request As WebRequest = DirectCast(WebRequest.Create(strUrl), HttpWebRequest)
Dim strResponse As String = ""
Dim byteAuth() As Byte = Encoding.UTF8.GetBytes(InternalSettings.APIkey & ":" & InternalSettings.APIpwd)
Dim strPost As String = "SaveAllCustomersData=false"    
Dim bytePost() As Byte = Encoding.UTF8.GetBytes(strPost)

request.ContentType = "application/x-www-form-urlencoded"
request.Method = "PUT"
request.Headers.Add("Authorization", "Basic " & Convert.ToBase64String(byteAuth))

Using sw = New StreamWriter(request.GetRequestStream())
  sw.Write(bytePost, 0, bytePost.Length)
  sw.Flush()

  Using response As HttpWebResponse = request.GetResponse()
    Using sr = New StreamReader(response.GetResponseStream())
      strResponse = sr.ReadToEnd()
    End Using
  End Using

End Using