您可以将其设置如下，

 await blobClient.UploadAsync(stream, true, default);
 await blobClient.SetHttpHeadersAsync(new BlobHttpHeaders
 {
    ContentType = contentType
 });

编辑:如评论中所述，一种有效的方法可通过以下一种方法完成操作，

As mentioned in the comment, the efficient way to do the same with a single method as follows,

await blobClient.UploadAsync(ms, new BlobHttpHeaders{ ContentType = "text/plain"});