要回显Jon(一个人并不完全不同意Jon)，请不要将async/await世界与pre-async/await(ContinueWith)混合使用世界.

To echo Jon (one does not simply disagree with Jon), do not mix the async/await world with the pre-async/await (ContinueWith) world.

要以字符串形式获取响应正文，您需要第二次等待:

To get the response body as a string you need a 2nd await:

var response = await client.PostAsync(fileUploadUrl, content);
response.EnsureSuccessStatusCode();
var body = await response.Content.ReadAsStringAsync();