使用多个参数注册DbContext [英] registering DbContext with multiple parameters

问题描述

我正在尝试将TenantProvider注入DbContext

 公共类AppDbContext：IdentityDbContext< ApplicationUser，ApplicationRole，long> 
 {
 public int？ _tenantId; 
 
公共ITenantProvider _tenantProvider； 
 
 public AppDbContext（
 DbContextOptions< AppDbContext>选项，
 ITenantProvider tenantProvider 
）
：基本（选项）
 {
 _tenantProvider = tenantProvider; 
} 
  

但我不知道如何正确注册-如果我将构造函数中的断点- tenantProvider 为 null 。

Startup.cs

  services.AddDbContext< AppDbContext>（选项=> AppDbContextOptionsBuilder.Get（））; 
  

下一行需要注入 DbContext 添加到控制器或服务中（如果我将 ServiceLifetime.Scoped 添加为上述方法的第二个参数- AddDbContext -该功能无效）：

  services.AddScoped（p => new AppDbContext（AppDbContextOptionsBuilder.Get（）， p.GetService< ITenantProvider>（）））； 
  

（ Entity Framework 是我的解决方案）

---

使用 .AddScoped 方法时-通过使用 .GetService 方法解析 TenantProvider 进入构造函数。

有人知道如何在 .AddDbContext 方法中解析 TenantProvider 吗？

其他信息：

我正尝试替换 DbContext 的构造函数中的 ITenantProvider 和 IHttpContextAccessor -后者注册为单例。但是 acessor 参数仍然为 null 。

services.AddSingleton< IHttpContextAccessor，HttpContextAccessor>（）;

解决方案

我不不太了解您的 AddScoped 调用应该做什么。 AddDbContext 已经在服务集合中正确注册了数据库上下文。因此，当您通过依赖项注入解决上下文时，其他依赖项将被自动解决。

因此，这样做应该足够了：

  services.AddDbContext< AppDbContext>（options =>…）; 
 
服务。AddSingleton< ITenantProvider，TenantProvider>（）; 
  

然后，您可以依赖您的 AppDbContext 使用构造函数注入，例如

---

不过有两个注释：

1. 在配置选项时，应修改所传递的选项对象。因此，您不应该只返回 AppDbContextOptionsBuilder.Get（），而是使用传递的选项对象并对其进行编辑。




2. 您应该真正考虑依赖于租户提供者的数据库上下文是否正确。根据 SRP ，您的数据库只能做一件事，并且可以提供数据库访问权限。 / p>
   
   

   根据租户提供者如何影响数据库访问，将这种依赖关系上移到同时使用数据库上下文和租户提供者的某些服务中可能更有意义以正确的方式查询数据。

I'm trying to inject TenantProvider into DbContext

public class AppDbContext : IdentityDbContext<ApplicationUser, ApplicationRole, long>
{
    public int? _tenantId;

    public ITenantProvider _tenantProvider;

    public AppDbContext(
        DbContextOptions<AppDbContext> options,
        ITenantProvider tenantProvider
        )
    : base(options)
    {
        _tenantProvider = tenantProvider;
    }

but I don't understand how to register it correctly - if I put the breakpoint in the constructor - tenantProvider is null.

The bit from Startup.cs

services.AddDbContext<AppDbContext>(options => AppDbContextOptionsBuilder.Get());

the next line is required to inject the DbContext into a controller or a service (if I add ServiceLifetime.Scoped as a second parameter to the method above - AddDbContext - the feature doesn't work):

services.AddScoped(p => new AppDbContext(AppDbContextOptionsBuilder.Get(), p.GetService<ITenantProvider>()));

(Entity Framework is a separate project in my solution)

---

When using .AddScoped method - we can pass TenantProvider into constructor by resolving it using .GetService method.

Does anyone have an idea of how to resolve TenantProvider in .AddDbContext method?

Additional info:

I was trying to replace ITenantProvider in the constructor of DbContext with IHttpContextAccessor - the latter is registered as singleton. But the acessor parameter is still null.

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

解决方案

I don’t really understand what your AddScoped call is supposed to do. AddDbContext will already register the database context properly with the service collection. So when you resolve the context through dependency injection, additional dependencies will be automatically resolved.

So it should be enough to do this:

services.AddDbContext<AppDbContext>(options => …);

services.AddSingleton<ITenantProvider, TenantProvider>();

And then, you can depend on your AppDbContext using constructor injection, e.g. in your controllers.

---

Two notes though:

1. When configuring options, you should modify the passed options object. So you should not just return AppDbContextOptionsBuilder.Get() but instead use the passed options object and edit that.

2. You should really think about whether your database context having a dependency on your tenant provider is the right thing to do. As per SRP, your database should only do a single thing and that is provide database access.

   Depending on how your tenant provider affects your database access, it might make more sense to move this dependency up one level into some service that uses both the database context and the tenant provider to query data in the right way.

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