等待异步完成之前的函数 returns

Question

我正在尝试通过 SendGrid API 发送 2 封电子邮件。有时 0 发送，有时 1 发送，有时两者都发送。该功能似乎没有等待承诺。我怎样才能修复它，让它始终发送两封电子邮件？

我的函数如下所示：

private async Task<bool> SendMails(string email, string name, string pdfPath, string imgPath)
{
    var client = new SendGridClient(_config["SendGrid:Key"]);
    bool messagesSent = false;
    var messageClient = new SendGridMessage
    {
        From = new EmailAddress(_config["SendGrid:Recipient"]),
        Subject = "Testmail",
        HtmlContent = _textManager.Get("getMailHtml")
    };

    var messageSecondClient = new SendGridMessage
    {
        From = new EmailAddress(_config["SendGrid:Recipient"]),
        Subject = "Second Testmail",
        HtmlContent = _textManager.Get("getSecondMailHtml")
    };

    messageClient.AddTo(email, name);
    messageSecondClient.AddTo(email, name);

    string[] fileListClient = new string[] { pdfPath };
    string[] fileListSecond = new string[] { pdfPath, imgPath };

    foreach (var file in fileListClient)
    {
        var fileInfo = new FileInfo(file);

        if (fileInfo.Exists)
            await messageClient.AddAttachmentAsync(fileInfo.Name, fileInfo.OpenRead());
    }

    foreach (var file in fileListSecond)
    {
        var fileInfo = new FileInfo(file);

        if (fileInfo.Exists)
            await messageSecondClient.AddAttachmentAsync(fileInfo.Name, fileInfo.OpenRead());
    }

    var responseClient = await client.SendEmailAsync(messageClient);
    var responseSecond = await client.SendEmailAsync(messageSecondClient);

    if (responseClient.StatusCode.ToString() == "202" && responseSecond.StatusCode.ToString() == "202")
    {
        messagesSent = true;
    }
    return messagesSent;
}

我是这样称呼它的：

            Task<bool> sendMails = await Task.FromResult(SendMails(formCollection["email"], formCollection["name"], pdfPath, imgPath));

            if (!sendMails.Result)
            {
                errorMessage = "Error sending mails.";
            }

Answer 1

您正在阻塞异步任务：

if (!sendMails.Result)

这可以cause a deadlock。使用 await.

而不是阻塞

你也可以去掉 await Task.FromResult，isn't doing anything at all:

bool sentMails = await SendMails(formCollection["email"], formCollection["name"], pdfPath, imgPath);

if (!sentMails)
{
  errorMessage = "Error sending mails.";
}

Answer 2

Task.FromResult returns 已经完成的 new Task，而不是从 [=14= 返回的 Task ].

没有任何事情等待 SendMails 完成。

只需等待方法返回的Task：

bool result = await SendMails(formCollection["email"], formCollection["name"], pdfPath, imgPath);

await 关键字为您解包 Task.Result。

等待异步完成之前的函数 returns

Function returns before await async finishes

.net

c#

asynchronous

sendgrid

async-await