请问AddressOf这个回调指针，怎么使用？我现在用阿里云oss上传文件，想上传时显示进度条，里面有这个东西，实在看不懂 - 专家坐堂 - Foxtable(狐表) - 新一代数据库软件，完美融合Access、Foxpro、Excel、vb.net之优势，人人都能掌握的快速软件开发工具!

Try

dim accessKeyId As String = Config.AccessKeyId

dim accessKeySecret As String = Config.AccessKeySecret

dim endpoint As String = Config.Endpoint

dim client As OssClient = New OssClient(endpoint, accessKeyId, accessKeySecret)

dim key As String = "GetObjectSample"

dim fileToUpload As String = Config.FileToUpload

dim dirToDownload As String = Config.DirToDownload

dim _event As AutoResetEvent = New AutoResetEvent(False)

client.PutObject(bucketName, key, fileToUpload)

Dim result = client.GetObject(bucketName, key)

Using requestStream = result.Content

Using fs = File.Open(dirToDownload & "/sample.data", FileMode.OpenOrCreate)

Dim length As Integer = 4 * 1024

Dim buf = New Byte(length - 1) {}

length = requestStream.Read(buf, 0, length)

fs.Write(buf, 0, length)

Loop While length <> 0

End Using

Console.WriteLine("Get object succeeded")

Catch ex As OssException

Console.WriteLine("Failed with error code: {0}; Error info: {1}. " & vbLf & "RequestID:{2}" & vbTab & "HostID:{3}", ex.ErrorCode, ex.Message, ex.RequestId, ex.HostId)

Catch ex As Exception

Console.WriteLine("Failed with error info: {0}", ex.Message)

End Try

主题：请问AddressOf这个回调指针，怎么使用？我现在用阿里云oss上传文件，想上传时显示进度条，里面有这个东西，实在看不懂