求救：我的上传怎么都不成功，老是发生异常（C）

代码如下：

private void buttonUpLoad_Click(object sender, EventArgs e)
        {
            String bucketName = "pmsoft_123";
            OpenFileDialog openFileDlg = new OpenFileDialog();
            openFileDlg.Title = "请选择上传的文件";
            if (DialogResult.OK != openFileDlg.ShowDialog())
            {
                return;
            }
            string fileToUpload = openFileDlg.FileName;
            string[] uploadInfoArr = fileToUpload.Split('\\');
            string sUpLoadNamme = uploadInfoArr[uploadInfoArr.Length - 1];//获取选择的文件名称
            ObjectMetadata metadata = new ObjectMetadata();
            // 可以设定自定义的metadata。
            //     metadata.UserMetadata.Add("myfield", "test");
            ClientConfiguration clientConfig = new ClientConfiguration();
            clientConfig.ConnectionTimeout = 3600 * 1000;
            OssClient ossClient = new OssClient(new Uri(ossEndpoint), accessId, accessKey, clientConfig);
            using (var fs = File.Open(fileToUpload, FileMode.Open))
            {
                ossClient.PutObject(bucketName, sUpLoadNamme, fs, metadata);
            }
            MessageBox.Show("上传成功!");
        }

发生异常：已添加了具有相同键的项