异常信息：
An unhandled exception was thrown by the application.
System.ObjectDisposedException: Cannot access a disposed object. A common cause of this error is disposing a context that was resolved from dependency injection and then later trying to use the same context instance elsewhere in your application. This may occur if you are calling Dispose() on the context, or wrapping the context in a using statement. If you are using dependency injection, you should let the dependency injection container take care of disposing context instances.
遇到这种情况一般是异步、同步混着调用了。
检查一下调用的地方是否为同步，但在实现函数里用异步得写法了。