.NET: app.Lifetime.ApplicationStopping.Register 中的依赖注入问题

Program.cs 中下面的代码

app.Lifetime.ApplicationStopping.Register(async () =>
{
    await app.Services.GetRequiredService<IRedisDatabase>().RemoveAsync(blogPostCacheKey);
    await app.Services.GetRequiredService<IRedisClientFactory>()
        .GetRedisClient("redis-postbody")
        .GetDbFromConfiguration()
        .RemoveAsync(postBodyCacheKey);
});

在运行时会报错，错误信息如下

The active test run was aborted. Reason: Test host process crashed : Unhandled exception. System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'IServiceProvider'.
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ThrowHelper.ThrowObjectDisposedException()
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(ServiceIdentifier serviceIdentifier, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)

请问如何解决这个问题？

回答

app.Lifetime.ApplicationStopping.Register(async () 不要异步. 它接受的是一个action. 内部callback 这个action的时候不会判断是不是返回了Task, 要不要await.

app.Lifetime.ApplicationStopping.Register( ()=>{

….RemoveAsync().GetAwaiter().GetResult(); 差不多这样子.

})

或者
await app.RunAsync()
// cleanup
await app.Service…..RemoveAsync(); 这样也行. 只要app没有dispose, 就都能用.