ef core An attempt was made to use the context while it is being configured.

报错信息：

System.InvalidOperationException: An attempt was made to use the context while it is being configured. A DbContext instance cannot be used inside OnConfiguring since it is still being configured at this point. This can happen if a second operation is started on this context before a previous operation completed. Any instance members are not guaranteed to be thread safe.

我在前台同时请求两个后台接口，然后发现经常会出现一个接口正常而另一个接口报错的问题。查询网上资料后，一个解决方法是把Startup文件里配置数据库的 context生命周期改为每次请求都实例化一下。我更改之后，刷新了几次页面发现这个改法可行。不过过了一会儿，我再次刷新页面时，发现原来那个问题又出现了，也就是说问题没有解决。

一次偶然间，我突然发现我的_context 定义的是静态类...我人傻了，改为非静态来之后，可以了。