使用多个DbContext的实体框架核心 [英] Entity Framework Core Using multiple DbContexts

问题描述

我遇到一个问题，当我尝试访问我的PartsDbContext中的字段时，出现以下错误：

I'm having a problem that when I try to access a field in my PartsDbContext I get the following error:

系统。 Data.SqlClient.SqlException：'无效的对象名称'fieldName'

System.Data.SqlClient.SqlException: 'Invalid object name 'fieldName''

似乎这是因为我试图使我的PartsDbContext使用与与Identity一起使用的ApplicationDbContext相同的数据库。我需要知道如何设置第二个dbcontext以与使用/创建其他数据库的EF核心一起使用。

It seems that this is because I'm trying to make my PartsDbContext use the same database as my ApplicationDbContext which is used with Identity. I need to know how to setup a 2nd dbcontext to work with EF core that uses/creates a different database.

我尝试创建第二个连接字符串，但这使我收到此错误：

I've tried creating a 2nd connection string but that gets me this error:

System.Data.SqlClient.SqlException：'无法打开登录请求的数据库 PartsDb。登录失败。
用户'DESKTOP-4VPU567\higle'的登录失败。

System.Data.SqlClient.SqlException: 'Cannot open database "PartsDb" requested by the login. The login failed. Login failed for user 'DESKTOP-4VPU567\higle'.'

这是我的代码：

appsettings.json

"ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=aspnet-PrecisionCustomPC-b14db89e-86ad-4855-a17f-ac64a04339aa;Trusted_Connection=True;MultipleActiveResultSets=true",
    "PartsConnection":  "Server=(localdb)\\mssqllocaldb;Database=PartsDb"
},
"Logging": {
    "IncludeScopes": false,
    "LogLevel": {
        "Default": "Warning"
    }
}

PartsDbContext.cs

public class PartsDbContext : DbContext
{
    public DbSet<PartsViewModels.Tower> Towers { get; set; }
    public DbSet<PartsViewModels.Motherboard> Motherboards { get; set; }

    public PartsDbContext(DbContextOptions<PartsDbContext> options)
        : base(options)
    {
    }
}

Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddDbContext<ApplicationDbContext>(options =>
         options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

    services.AddIdentity<ApplicationUser, IdentityRole>()
        .AddEntityFrameworkStores<ApplicationDbContext>()
        .AddDefaultTokenProviders();

    services.AddEntityFramework()
        .AddDbContext<PartsDbContext>(options =>
          options.UseSqlServer(Configuration.GetConnectionString("PartsConnection")));

    services.AddMvc();

    services.AddAuthorization(options =>
    {
        options.AddPolicy("RequireAdminRole", policy => policy.RequireRole("Admin"));
    });

    // Add application services.
    services.AddTransient<IEmailSender, AuthMessageSender>();
    services.AddTransient<ISmsSender, AuthMessageSender>();
}

AdminController.cs

[Authorize(Policy = "RequireAdminRole")]
public class AdminController : Controller
{
    private readonly PartsDbContext _context;

    public AdminController(PartsDbContext context)
    {
        _context = context;
    }

    public IActionResult Index()
    {
        return View();
    }

    public IActionResult Towers()
    {
        var model = _context.Towers.ToList();
        return View(model);
    }
}

线 var model = _context.Towers.ToList（）; 出现错误。

再次。我想将我的PartsDbContext设置为与Entity Framework Core一起使用，以便EF-Core可以自动创建数据库。

Once again. I want to setup my PartsDbContext to work with Entity Framework Core in a way that EF-Core will automatically create the database.

推荐答案

我想到了。这主要是因为我不小心删除了Identity正在使用的数据库，因此我需要弄清楚如何找回它。

I figured it out. This mostly came about because I accidentally deleted the database that Identity was using and I needed to figure out how to get it back.

显然，我的连接字符串没有错这样。我只需要进入软件包管理器并按以下顺序键入以下命令：

Apparently there's nothing wrong with my connection string the way it is. I just needed to go into the package manager and type these commands in this order:

1. 添加迁移init-上下文PartsDbContext


2. 更新数据库-Context PartsDbContext

1. Add-Migration init -Context PartsDbContext
2. Update-Database -Context PartsDbContext

我发现了这一点，因为这是使ApplicationDbContext再次工作所要做的，事实证明，当您创建新的MVC Core Web Application时，此步骤已为您完成在Visual Studio中使用个人用户身份验证。

I found this out because that is what I had to do to get my ApplicationDbContext working again and it turns out that this step is done for you when you create a new MVC Core Web Application in Visual Studio using Individual User Authentication.

因此，基本上，添加更多DbContext的步骤是：

So basically the steps for adding more DbContexts is to:

1. 创建DbContext类


2. 在 appsettings.json
中为该DbContext创建连接字符串在 Startup.cs

3. 将DbContext添加到已配置的服务中。在将使用它的控制器中设置DbContext。


4. 打开软件包管理器并运行上面的2行。 （如果 -Context不起作用，请尝试 --context


5. 运行程序，让EntityFrameworkCore负责其余的工作。

1. Create a DbContext Class
2. Create a Connection string for that DbContext in appsettings.json
3. Add the DbContext to your configured services in Startup.cs
4. Setup the DbContext in the controllers that will use it.
5. Open the package manager and run the 2 lines above. (if "-Context" doesn't work try "--context"
6. Run your program and let EntityFrameworkCore take care of the rest.

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