我如何在Blazor Server中将服务注入实体框架adddbContextFactory lambda函数？

Question

在Blazor Server中，如何将范围的服务注入下面的lambda，以便我可以阅读经过身份验证的用户并根据用户选择一个SQL连接字符串。

builder.Services.AddDbContextFactory<GlueDbContext>((provider, options) =>
    {
        var AuthenticationStateProvider = provider.GetService<AuthenticationStateProvider>();
        // *** Compiles but FAILS because AuthenticationStateProvider is not a Singleton ***
        var user = _authenticationStateProvider.GetAuthenticationStateAsync().Result.User;
        //
        string sqlConnectString = SomeFunctionDerivingTheConnectionFromTheUser(user);
        options.UseMySql(connectionString);
    });

Answer 1

以下 this IDE因此可能包含一些错别字）：

var serviceScopeFactory = provider.GetService<IServiceScopeFactory>(); //IServiceScopeFactory is a singleton, so you can easily get it here
using var scope = serviceScopeFactory.CreateScope();
var authenticationStateProvider = scope.GetService<AuthenticationStateProvider>();
//...

Answer 2

你不能那样做。 Services.Add ....只是将类/接口添加到集合中。直到后来，服务容器才开始初始化，直到您使用DI对象之前，该对象的实例才会初始化。

为了说明过程，这是测试中设置服务容器的代码。

        var services = new ServiceCollection();
        services.AddDbContextFactory<InMemoryWeatherDbContext>(options => options.UseInMemoryDatabase("WeatherDatabase"));
        services.AddSingleton<IDataBroker, ServerDataBroker>();
        var serviceProvider = services.BuildServiceProvider();

无论您设计什么，都需要重新思考。在温泉会话初始化之前，您无法获得用户。

Answer 3

AddDbContextFactory在Singleton上具有默认参数集。
添加 servicelifetime.scoped

builder.Services.AddDbContextFactory<GlueDbContext>((provider, options) =>
    {
        var AuthenticationStateProvider = provider.GetService<AuthenticationStateProvider>();
        var user = _authenticationStateProvider.GetAuthenticationStateAsync().Result.User;
        string sqlConnectString = SomeFunctionDerivingTheConnectionFromTheUser(user);
        options.UseMySql(connectionString);
    }, ServiceLifetime.Scoped);