文件损坏的原因是由于以下代码行:

The reason your file is corrupted is because of the following line of code:

cloudFile.UploadFromStreamAsync(fileStream);

基本上，您正在启动一个异步过程，但不等待它完成.要解决此问题，您可以执行以下任一操作:

Essentially you're starting an async process but not waiting for it to complete. To fix, you could do either of the following:

使用此方法的sync版本:

cloudFile.UploadFromStream(fileStream);

或者，等待async方法完成(推荐):

Or, wait for async method to finish (recommended):

await cloudFile.UploadFromStreamAsync(fileStream);

请注意，如果您使用的是异步方法，则还需要使调用方法也异步.

Please note that if you're using async method, you would need to make the calling method async as well.