如何從 Asp.Net Core 的 ConfigureServices 方法中訪問添加到 DI 容器的服務

Question

下面的代碼示例來自 Startup.cs 中的 Asp.Net Core ConfigureServices方法。

我首先注冊了一個名為AppState的 singleton 服務。 之后，我正在配置 OpenIdConnect，在OnTokenValidated lambda 中，我需要訪問我剛剛在上面的 DI 容器中注冊的AppState服務。

訪問AppState服務實例最優雅的方式是什么？

如果可能的話，我寧願不要在ConfigureServices方法中調用services.BuildServiceProvider() 。

services.AddSingleton<AppState>();

services.Configure<OpenIdConnectOptions>(AzureADB2CDefaults.OpenIdScheme, options =>
{
    options.Events = new OpenIdConnectEvents
    {
        OnTokenValidated = async ctx =>
        {
            //How to get access to instance of AppState, 
            //which was added to DI container up above
            AppState appState = //{get from DI somehow}; 
            appState.DoSomething();
        }
    };
});

編輯：使用下面的答案，我像這樣編輯了代碼，但我可以確認 OnTokenValidated 事件沒有觸發，而不是我原來的問題中的上面的代碼，它確實觸發了：

services.AddOptions<OpenIdConnectOptions>(AzureADB2CDefaults.OpenIdScheme)
            .Configure<IServiceScopeFactory>((options, sp) => {
                using (var scope = sp.CreateScope())
                {
                    options.Events = new OpenIdConnectEvents
                    {
                        OnTokenValidated = async ctx =>
                        {
                            var appState = scope.ServiceProvider.GetRequiredService<AppState>();

                            await appState.Dosomething();         
                        }
                    };
                }
            });

Answer 1

使用TokenValidatedContext訪問當前請求服務提供者並解析服務

services
    .Configure<OpenIdConnectOptions>(AzureADB2CDefaults.OpenIdScheme, options => {
        options.Events = new OpenIdConnectEvents {
            OnTokenValidated = async ctx => {
                //Get access to instance of AppState, 
                //which was added to DI container up above
                AppState appState = ctx.HttpContext.RequestServices
                    .GetRequiredService<AppState>();
                await appState.DoSomething();

                //...
            }
        };
    });

Answer 2

您可以從事件上下文訪問 DI 服務：

services.AddSingleton<AppState>();

services.Configure<OpenIdConnectOptions>(AzureADB2CDefaults.OpenIdScheme, options =>
{
    options.Events = new OpenIdConnectEvents
    {
        OnTokenValidated = async ctx =>
        {
            var appState = (AppState)ctx.HttpContext.RequestServices.GetService(typeof(AppState));
            appState.DoSomething();
        }
    };
});

Answer 3

調用services.Configure<T> ，將IConfigureOptions<T>添加到調用您的操作方法的服務容器中； https://github.com/aspnet/Options/blob/master/src/Microsoft.Extensions.Options/OptionsServiceCollectionExtensions.cs#L72

您可以定義自己的IConfigureOptions<T>實現並注入您喜歡的任何服務。