如何使用 webservice C# 为基于事件的函数应用 async/await？

Question

我正在尝试使用网络服务从第三方调用数据，加载数据需要很长时间，所以我需要应用 async/await对于该方法，我在 .cs 中调用该方法，我正在使用如下所示，当我尝试使用“Void”而不是“Task”时，如果我需要很长时间才能加载使用任务事件不会触发。

 [WebMethod]
    public List<SuggestedItemsInput> SaveSuggestedItems(string emailbody, string OrderHeaderID)
    {
        List<SuggestedItemsInput> result = null;

        //... passing header and neccesery things

        request.AddParameter("application/text; charset=utf-8", strFinalEmail, ParameterType.RequestBody);
        IRestResponse restResponse = client.Execute(request);

        result = JsonConvert.DeserializeObject<List<SuggestedItemsInput>>(restResponse.Content);


        //Save to database
        if (dtProducts.Rows.Count >= 1)
            dalPendingOrders.SaveSuggestedItems(dtProducts);
        LogMessage("Suggested Items for " + OrderHeaderID + " : " + products.Products.Count);

        return result;
    }

在.cs中

  protected void btnClaim_Click(object sender, EventArgs e)
    {
        GetSuggestedItemsFromService();
    }

    private async void GetSuggestedItemsFromService()
    {
        List<SuggestedItemsInput> suggestedItems = await Task.Run(() => SaveAndGetSuggestedItemAsync());

        ViewState["sItems"] = suggestedItems;
        if (suggestedItems != null && suggestedItems.Count > 0)
        {
            GetSuggestedItems(Request["OrderRecordID"].ToString());
            lblInfo.Text = string.Empty;
        }
    }
    private List<SuggestedItemsInput> SaveAndGetSuggestedItemAsync()
    {
        OHDWebService OHDService = new OHDWebService();
        List<SuggestedItemsInput> suggestedItemsList = OHDService.SaveSuggestedItems(hdnPlainBody.Value, hfdOrderRecordID.Value);
        return suggestedItemsList;
    }

    private void GetSuggestedItems(string OrderRecordID)
    {
        dt = dalPendingOrders.GetSuggestedItems(OrderRecordID);
        if (dt.Rows.Count > 0)
        {
            grdSuggestedItems.DataSource = dt;
            grdSuggestedItems.DataBind();
        }
        else
        {
            lblInfo.Text = "No Data Found";
        }
    }

Answer 1

使用 ASP.NET Web 窗体，您必须将异步代码注册为页面任务：

protected void btnClaim_Click(object sender, EventArgs e)
{
    RegisterAsyncTask(GetSuggestedItemsFromService);
}

private async Task GetSuggestedItemsFromService()
{
    List<SuggestedItemsInput> suggestedItems = await SaveAndGetSuggestedItemAsync();

    ViewState["sItems"] = suggestedItems;
    if (suggestedItems != null && suggestedItems.Count > 0)
    {
        GetSuggestedItems(Request["OrderRecordID"].ToString());
        lblInfo.Text = string.Empty;
    }
}

查看这篇文章：

Using Asynchronous Methods in ASP.NET 4.5

不要在 ASP.NET 应用程序中使用Task.Run。它会使用更多的资源，而且会更慢。

Answer 2

您需要使您的 btnClaim_Click 方法异步无效，然后等待 GetSuggestedItemsFromService，它应该返回一个任务。仅将 async void 用于事件处理程序。您的 .cs 代码应如下所示：

protected async void btnClaim_Click(object sender, EventArgs e)
    {
        await GetSuggestedItemsFromService();
    }

    private async Task GetSuggestedItemsFromService()
    {
        List<SuggestedItemsInput> suggestedItems = await Task.Run(() => SaveAndGetSuggestedItemAsync());

        ViewState["sItems"] = suggestedItems;
        if (suggestedItems != null && suggestedItems.Count > 0)
        {
            GetSuggestedItems(Request["OrderRecordID"].ToString());
            lblInfo.Text = string.Empty;
        }
    }
// Rest of your code

此外，如果它实际上是异步的，则约定是仅调用异步方法。因此，我建议将 SaveAndGetSuggestedItemAsync() 重命名为 SaveAndGetSuggestedItem()（它没有 async 关键字）。