vb中的Dropnet代码无法正常工作

Question

我尝试使用dropnet在vb上的Dropbox上进行文件上传，但不起作用。结果出现以下错误：收到响应[未授权]：预计会看到[确定]。 HTTP响应是[{＆＃34;错误＆＃34;：＆＃34;未找到请求令牌。＆＃34;}] 这是我的代码：

_client = New DropNetClient("xxxxxxx", "xxxxxxx")
   Dim login As UserLogin = _client.GetToken()
   _client.UserLogin = login
   Dim url = _client.BuildAuthorizeUrl()
   Process.Start(url)
Dim tokenAcess = _client.GetAccessToken()
        _client.GetAccessTokenAsync(Function(accessToken)
           _client = New DropNetClient("xxxxxx", "xxxxxx", tokenAcess)
           End Function, Function([error])                                                      MessageBox.Show([error].Message)

        End Function)
   Try
    Dim rawData As Byte() = File.ReadAllBytes("c:\image.png")
     Dim result As MetaData = _client.UploadFile("/", "image.png", rawData)
     MessageBox.Show("Successfully uploaded to Dropbox.", "Uploaded to Dropbox")
   Catch dropboxEx As Exception
     MessageBox.Show("Error: " + dropboxEx.Message)
  End Try