自从asp.net升级到net7.0后，我的www.example.com网站出现了问题。
我将一个pdf加载到临时目录中，并想将其附加到电子邮件中。

// upload invoice to computer
        var httpClient = new HttpClient();
        var responseStream = await httpClient.GetStreamAsync("..site.com/.../uploads/" + invoice.PfadRel + "");
        using var fileStream = new FileStream(@"C:\Temp\Invoice-" + invoice.no + ".pdf", FileMode.Create, (FileAccess)FileShare.ReadWrite);
        responseStream.CopyTo(fileStream);

        // attach invoice to mail
        builder.Attachments.Add(@"C:\Temp\Invoice-" + invoice.no + ".pdf");

不幸的是，带有“builder.Attachments.”的行生成错误消息：

IOException: The process cannot access the file because it is being used by another process.

有人知道这里出了什么问题吗？