A second operation was started on this context before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext.

 A second operation was started on this context before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext. 

在Blazor Server應用中有時候因為撰寫非同步的處理

可能會將原本DB相關存取服務(設置的生命週期:Scoped)

會有此例外發生在某些時候

在asp.net core3.1版本

我們可以藉由

引用命名空間

using Microsoft.Extensions.DependencyInjection;

並且確立只要該服務存取相同的DbContext

有呼叫存取的地方全部都要改為如下寫法

假設該頁有兩隻Service都存取相同DbContext就建議都統一調整

1 2 3 4 5 6 7 8 9 10 11

using (var scope = this.serviceProvider.CreateScope()) { var tmpAAA_Service = scope.ServiceProvider.GetRequiredService<AAA_Service>(); AAAData = tmpAAA_Service.GetOne(); } using (var scope = this.serviceProvider.CreateScope()) { var tmpBBB_Service = scope.ServiceProvider.GetRequiredService<BBB_Service>(); List<BBBData> lsBData = tmpBBB_Service.GetAll(); }

其他高手也遇到類似的問題

https://rainmakerho.github.io/2020/09/13/2020020/