使用任務運行（異步）響應中的部分視圖更新UI

Question

我正在使用MVC C＃Razor Framework 4.6。

我有靜態方法ExportManager.ExportExcelCannedReportPPR包裝在Task.Run長期運行的報告。此方法返回boolean值並基於此我刷新部分視圖（_NotificationPanel）。

public ActionResult ExportCannedReport(string cannedReportKey, string cannedReportName) 
{    
    string memberKeys = _curUser.SecurityInfo.AccessibleFacilities_MemberKeys; //ToDo: Make sure this is fine or need to pass just self member? 
    string memberIds = _curUser.SecurityInfo.AccessibleFacilities_MemberIDs; //ToDo: Make sure this is fine or need to pass just self member? 
    string curMemberNameFormatted = _curUser.FacilityInfo.FacilityName.Replace(" ", string.Empty); 
    string cannedReportNameFormatted = cannedReportName.Replace(" ", string.Empty); 
    string fileName = string.Concat(cannedReportNameFormatted, "_", DateTime.Now.ToString("yyyyMMdd"), "_", curMemberNameFormatted); 
    //ToDo: Make sure below getting userId is correct 
    string userId = ((_curUser.IsECRIStaff.HasValue && _curUser.IsECRIStaff.Value) ? _curUser.MembersiteUsername : _curUser.PGUserName); 

    var returnTask = Task.Run<bool>(() => ExportManager.ExportExcelCannedReportPPR(cannedReportKey, cannedReportName, fileName, memberIds, userId)); 
    returnTask.ContinueWith((antecedent) => 
    { 
     if (antecedent.Result == true) 
     { 
      return PartialView("_NotificationPanel", "New file(s) added in 'Download Manager'."); 
     } 
     else 
     { 
      return PartialView("_NotificationPanel", "An error occurred while generating the report."); 
     } 
    }, TaskContinuationOptions.OnlyOnRanToCompletion); 

    return PartialView("_NotificationPanel", ""); 
} 

現在的問題是，即使在_NotificationPanel得到ContinueWith執行UI沒能刷新。

Answer 1

問題是，一旦你從它返回 - 該請求完成。對於單個請求，您無法多次返回。請求和響應是1比1。您需要在此處使用async和await，以便在導出完成後才返回結果。

public async Task<ActionResult> ExportCannedReport(string cannedReportKey, 
                string cannedReportName) 
{    
    // Omitted for brevity... 

    var result = 
     await Task.Run<bool>(() => 
      ExportManager.ExportExcelCannedReportPPR(cannedReportKey, 
                cannedReportName, 
                fileName, 
                memberIds, 
                userId)); 

    return PartialView("_NotificationPanel", 
     result 
      ? "New file(s) added in 'Download Manager'." 
      : "An error occurred while generating the report."); 
} 

你需要使該方法返回Task這樣，這是「awaitable」。然後您將該方法標記爲async，該關鍵字啓用await關鍵字。最後，您準備好執行長時間運行的任務，並從結果中正確地確定並返回所需的局部視圖更新。

更新

或者，可以一旦服務器響應利用客戶端和更新上的AJAX調用。有關具體結帳的詳細信息，請參閱MSDN。