Asp.net mvc 如何在ASP.NET MVC控制器中调用异步方法？

我试图在ASP.NET MVC控制器中调用

async

方法，但遇到异常：

此时无法启动异步操作。异步操作只能在异步处理程序或模块内启动，或在页面生命周期中的某些事件期间启动。如果在执行页面时发生此异常，请确保已标记该页面。此异常还可能表示有人试图调用“async void”方法，这在ASP.NET请求处理中通常不受支持。相反，异步方法应该返回一个任务，调用方应该等待它

我的代码：

控制器：

[HttpGet]
public ActionResult OfferDetailsPage(string id)
{
    // string userid = ClaimsPrincipal.Current.FindFirst(ClaimTypes.Name).Value.ToString();
    // var u_role = db.UserDetails.Where(x => x.ADID == userid).FirstOrDefault();
    // if (u_role == null)
    // {
    //    return RedirectToAction("Unauthorize", "Account");
    // }
    // else if (u_role.TypeOfUser.ToLower() != "validator")
    // {
    //    return RedirectToAction("Unauthorize", "Account");
    // }

    ProductOfferDetails model = new ProductOfferDetails();

    AssignedOffersImplementation offerdetail_ = new AssignedOffersImplementation();

    DataSet dstProductlist = offerdetail_.GetOfferSubmittedById(id);

    if(dstProductlist.Tables[0].Rows[0]["status"].ToString()!="Active")
    {
        return Content("Offer moved from here..");
    }

    model.Offer_UOID = dstProductlist.Tables[0].Rows[0]["Offer_UOID"].ToString();
    model.OfferId = dstProductlist.Tables[0].Rows[0]["Offer_Id"].ToString();
    model.ProductURL = dstProductlist.Tables[0].Rows[0]["Offer_pgURL"].ToString();
    // string ProductURL = dstProductlist.Tables[0].Rows[0]["Offer_pgURL"].ToString();
    model.DatePublication = Convert.ToDateTime(dstProductlist.Tables[0].Rows[0]["Date_Publication"].ToString());
    // model.SoldDate = Convert.ToDateTime(dstProductlist.Tables[0].Rows[0]["Date_Sold"].ToString());
    model.OfferStatus = dstProductlist.Tables[0].Rows[0]["OfferStatus"].ToString();
    model.SellerComments = dstProductlist.Tables[0].Rows[0]["Seller_Comments"].ToString();
    model.Product_Title = dstProductlist.Tables[0].Rows[0]["Product_Title"].ToString();
    model.Offer_Sk = dstProductlist.Tables[0].Rows[0]["Offer_Sk"].ToString();
    model.ProductSN = dstProductlist.Tables[0].Rows[0]["ProductSN"].ToString();
    // model.ImageURL = dstProductlist.Tables[0].Rows[0]["Image_url"].ToString();
    model.SNSticker = dstProductlist.Tables[0].Rows[0]["SN_sticker"].ToString();
    model.CH_Fashion_Intranet = dstProductlist.Tables[0].Rows[0]["CH_Fashion_Intranet"].ToString();
    // model.SNTag = dstProductlist.Tables[0].Rows[0]["SN_Tag"].ToString();
    model.SNCard = dstProductlist.Tables[0].Rows[0]["SN_Card"].ToString();
    // model.ValidatorComments = dstProductlist.Tables[0].Rows[0]["Validator_Comments"].ToString();
    // model.IntialSN = dstProductlist.Tables[0].Rows[0]["Initial_SN"].ToString();
    model.SNComments = dstProductlist.Tables[0].Rows[0]["SN_comments"].ToString();
    model.SNCertificate = dstProductlist.Tables[0].Rows[0]["SN_Certificate"].ToString();
    // model.DateIdentification = dstProductlist.Tables[0].Rows[0]["DateIdentification"].ToString();
    model.Offer_UOID = dstProductlist.Tables[0].Rows[0]["Offer_UOID"].ToString();
    model.OfferId = dstProductlist.Tables[0].Rows[0]["Offer_Id"].ToString();
    model.ProductURL = dstProductlist.Tables[0].Rows[0]["Offer_pgURL"].ToString();
    string ProductURL = dstProductlist.Tables[0].Rows[0]["Offer_pgURL"].ToString();
    model.DatePublication = Convert.ToDateTime(dstProductlist.Tables[0].Rows[0]["Date_Publication"].ToString());
    model.SoldDate = (dstProductlist.Tables[0].Rows[0]["Date_Sold"].ToString());
    model.OfferStatus = dstProductlist.Tables[0].Rows[0]["OfferStatus"].ToString();
    // model.SellerComments = dstProductlist.Tables[0].Rows[0]["Seller_Comments"].ToString();
    model.Product_Title = dstProductlist.Tables[0].Rows[0]["Product_Title"].ToString();
    model.Offer_Sk = dstProductlist.Tables[0].Rows[0]["Offer_Sk"].ToString();

    // if (dstProductlist.Tables[0].Rows[0]["SNEnteredStatus"ToString() == "True")
    // {
    //    return Content("Offer Already Submitted");
    // };
    // model.ProductSN = dstProductlist.Tables[0].Rows[0]["ProductSN"].ToString();
    // model.ImageURL = dstProductlist.Tables[0].Rows[0]["Image_url"].ToString();
    // model.SNSticker = dstProductlist.Tables[0].Rows[0]["SN_sticker"].ToString();
    // model.CH_Fashion_Intranet = dstProductlist.Tables[0].Rows[0]["CH_Fashion_Intranet"].ToString();
    // model.SNTag = dstProductlist.Tables[0].Rows[0]["SN_Tag"].ToString();
    // model.SNCard= dstProductlist.Tables[0].Rows[0]["SN_Card"].ToString();
    // model.ValidatorComments = dstProductlist.Tables[0].Rows[0]["Validator_Comments"].ToString();
    // model.IntialSN = dstProductlist.Tables[0].Rows[0]["Initial_SN"].ToString();
    // model.SNComments = dstProductlist.Tables[0].Rows[0]["SN_comments"].ToString();
    // model.SNCertificate = dstProductlist.Tables[0].Rows[0]["SN_Certificate"].ToString();

    DataSet dstBlobImages = offerdetail_.BlobImages(model.Offer_Sk);
    IEnumerable<Models.BlobImages> _blobs = DataTableExtentions.ToList<Models.BlobImages>(dstBlobImages.Tables[0]);
    model.blobs = _blobs;

    IEnumerable<ProductOfferDetails> _Productimageslist = DataTableExtentions.ToList<ProductOfferDetails>(dstProductlist.Tables[0]);

    TempData["SN_Tag"] = model.SNTag;
    TempData["SN"] = model.ProductSN;
    TempData["CH_Fashion_Intranet"] = model.CH_Fashion_Intranet;
    TempData["SN_Certificate"] = model.SNCertificate;
    TempData["SN_Sticker"] = model.SNSticker;
    TempData["SN_Comments"] = model.SNComments;
    TempData["SN_Card"] = model.SNCard;

    string itemcode = string.Empty;
    string stylecode = string.Empty;

    GetORLIData(model.ProductSN);
    MakeRequest(model.ProductSN);

    if (Session["itemcode"] != null)
    {
        itemcode = Session["itemcode"].ToString();
        stylecode = Session["stylecode"].ToString();

        Session.Remove("itemcode");
        Session.Remove("stylecode");
    }

    // var photo = GetPhoto(model.ProductSN);
    ViewBag.itemcode = itemcode;
    ViewBag.stylecode = stylecode;

    return View(model);
}   

请给我建议在ASP.NET MVC控制器中调用异步方法，因为

MakeRequest（）

声明为

async

方法，调用该方法的控制器还必须具有

async

修饰符和

Task

返回类型，而不是普通的

ActionResult

，因为

async

方法不能与异常消息中提到的同步处理程序正常工作：

[HttpGet]
public async Task<ActionResult> OfferDetailsPage(string id)
{
    // other stuff

    // calling async method, this must be await-ed
    await MakeRequest(model.ProductSN);

    // other stuff

    return View(model);
}

---

异步无效方法真的很糟糕，你应该去了解一下。@DavidG，它们不错，如果你不关心

异步无效的结果，或者你不关心
异步无效是否引发异常，你可以使用它们…；）
MakeRequest
不需要返回任何内容，它可以是
Task
。
[HttpGet]
public async Task<ActionResult> OfferDetailsPage(string id)
{
    // other stuff

    // calling async method, this must be await-ed
    await MakeRequest(model.ProductSN);

    // other stuff

    return View(model);
}

var result = await MakeRequest(model.ProductSN);