在 ConfigureServices 之后添加身份

Question

我正在尝试在 ConfigureServices 方法之后添加身份。这是因为我在ConfigureServices 方法之外注册了dbContext。所以，现在我必须在配置dbContext 之后配置身份（同样，我已经在ConfigureServices 之外完成了）。我为dbContext 所做的就是创建了一个工厂并将其添加到ConfigureServices：

services.AddScoped<IDbContextFactory, DbContextFactory>();

然后我使用 DI 将它注入到我的控制器的构造函数中：

    private IDbContextFactory contextFactory;
    private AppDbContext context;

    public DbTestController(IDbContextFactory _contextFactory)
    {
        contextFactory = _contextFactory;
        context = contextFactory.Create(); //Create() returns an `AppDbContext`
    }

我能够对数据库执行 CRUD 操作，但是 Identity 不起作用，它会抛出异常：

No service for type Microsoft.AspNetCore.Identity.XXX has been registered

那是因为我在 ConfigureServices 中注册身份而没有先设置 dbContext （因为它是在 ConfigureServices 方法之后设置的。

services.AddIdentity<IdentityUser, IdentityRole>()
        .AddEntityFrameworkStores<AppDbContext>()
        .AddDefaultTokenProviders();

有没有办法像我设置 dbContext 一样设置身份？

编辑：DbContextFactory 包含一个返回AppDbContext 的Create 方法。它从一些配置文件中读取用户对数据库提供者的选择，相应地注册提供者，然后返回AppDbContext。以下是Create 方法的代码：

public AppDbContext Create()
    {
        //Get this value from some configuration
        string providerType = _configuration.GetValue<string>("DatabaseProvider");

        //and the connection string for the database
        string connectionString = _configuration.GetConnectionString(providerType);

        var dbContextBuilder = new DbContextOptionsBuilder();

        //Add some if else blocks here to check which provider to use
        //and then call dbContextBuilder.UseABC(connectionString)
        if (providerType == "MSSQL")
            dbContextBuilder.UseSqlServer(connectionString);
        else if (providerType == "SQLite")
            dbContextBuilder.UseSqlite(connectionString);


        //Create the context
        context = new AppDbContext(dbContextBuilder);

        return context;
    }

此方法从appsettings.json 读取providerType 和connectionString。该部分如下所示：

"DatabaseProvider": "MSSQL", //could be MySQL, SQLite etc etc
"ConnectionStrings": {
"MSSQL": "Server=(localdb)\\MSSQLLocalDB;Database=XXX_db;Trusted_Connection=True;MultipleActiveResultSets=true",
"SQLite": "Data Source=XXX_db.db"
 }

Answer 1

像往常一样在ConfigureServices 中注册上下文和身份，在启动时在组合根中应用所需的逻辑。

//Get this value from some configuration
string providerType = Configuration.GetValue<string>("DatabaseProvider");

//and the connection string for the database
string connectionString = Configuration.GetConnectionString(providerType);

services.AddDbContext<AppDbContext>(options => {
    if (providerType == "MSSQL")
        options.UseSqlServer(connectionString);
    else if (providerType == "SQLite")
        options.UseSqlite(connectionString);
});

services.AddIdentity<IdentityUser, IdentityRole>()
        .AddEntityFrameworkStores<AppDbContext>()
        .AddDefaultTokenProviders();

你需要做的是重新设计工厂

public class DbContextFactory : IDbContextFactory {

    private readonly Func<AppDbContext> factory;

    public DbContextFactory(Func<AppDbContext> factory) {
        this.factory = factory;
    }

    public AppDbContext Create() {
        return factory();
    }
}

并相应地向工厂代表注册

services.AddScoped<IDbContextFactory, DbContextFactory>(sp => 
    new DbContextFactory(() => sp.GetRequiredService<AppDbContext>()));