如何在 controller 中使用多个 DBContext

Question

如何在 controller 中使用多个 DBContext，我试图以不同的方式重载 construktors？

一些 Controller：

public C1(DBContext1 a, DBContext2 b, DBContext3 c)
{ 
}
 //public C1(DBContext1 a)
 //{ 
 //}
 //public C1(DBContext2 b)
 //{
 //}
 //public C1(DBContext3 c)
 //{
 //}

启动.cs：

services.AddDbContext<DBContext1>(options =>
options.UseSqlServer(new string(K.ConnectionString))
);

services.AddDbContext<DBContext2>(options =>
options.UseSqlServer(new string(K.ConnectionString))
);

services.AddDbContext<DBContext3>(options =>
options.UseSqlServer(new string(K.ConnectionString))
);

我找到了这个，但它似乎已经过时了

错误（，当前端调用构造函数时）：

执行请求时发生未处理的异常。

异常：System.InvalidOperationException：传递给 DBContext1 构造函数的 DbContextOptions 必须是 DbContextOptions。 注册多个 DbContext 类型时，请确保每个上下文类型的构造函数都具有 DbContextOptions 参数，而不是非泛型 DbContextOptions 参数。 在 Microsoft.EntityFrameworkCore.DbContext..ctor(DbContextOptions options) at _4_DWH.DBContext1..ctor(DbContextOptions options) 在 D:...\DBContext1.cs:line 43 at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments，签名 sig，Boolean 构造函数，Boolean wrapExceptions) 在 System.Reflection.RuntimeCultureConstructorInfo.Invoke，Object[BindingFlag]
在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context) 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor 2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor 2.VisitCallSite(ServiceCallSite callSite, TArgument 参数）在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope) 在 Mic rosoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.b__0（ServiceProviderEngineScope 范围）在 Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService（类型 serviceType，ServiceProviderEngineScope serviceProviderEngineScope）
在 Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService（类型 serviceType） 在 Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService（IServiceProvider sp，类型类型，类型 requiredBy，Boolean isDefaultParameterRequired）
在 lambda_method(Closure, IServiceProvider, Object[] ) 在 Microsoft.AspNetCore.Mvc.Controllers.ControllerActivatorProvider.<>c__DisplayClass4_0.b__0(ControllerContext controllerContext) 在 Microsoft.AspNetCore.Mvc.Controllers.ControllerFactoryProvider.<>c__DisplayClass5_0.g__CreateController|0( ControllerContext controllerContext) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Z27226C 864BAC7454A8504F8EDB15D95BZ isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc .Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync() --- 从先前引发异常的位置结束堆栈跟踪 --- 在 Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|17_0（ResourceInvoker 调用程序，任务任务，IDisposable 范围） Microsoft.AspNetCore.Routing.EndpointMiddleware.g__AwaitRequestTask|6_0（端点端点，任务 requestTask，ILogger 记录器）在 Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.MigrationsEndPointMiddleware.Invoke（HttpContext context）在 Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.Invoke（ HttpContext httpContext) 在 Microsoft.Asp NetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.Invoke(HttpContext httpContext) 在 Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

数据库上下文：

public class DBContext1 : DbContext
{
    // ...

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(new string(sameConnectionString));
    }

    public DBContext1() : base()
    {

    }

    public DBContext1(DbContextOptions options) : base(options)
    {
    }
}

Answer 1

1. 创建数据库上下文

public class DBContext_A : DbContext
{
    public DBContext_A(DbContextOptions<DBContext_A> options) : base(options)
    {
    }
}

public class DBContext_B : DbContext
{
    public DBContext_B(DbContextOptions<DBContext_B> options) : base(options)
    {
    }
}

public class DBContext_C : DbContext
{
    public DBContext_C(DbContextOptions<DBContext_C> options) : base(options)
    {
    }
}

2. 为每个 DBContext 定义一个连接字符串：

{
  "ConnectionStrings": {
    "Connection_A": "Server=(localdb)\\mssqllocaldb;Database=DB_A;Trusted_Connection=True;...",
    "Connection_B": "Server=(localdb)\\mssqllocaldb;Database=DB_B;Trusted_Connection=True;...",
    "Connection_C": "Server=(localdb)\\mssqllocaldb;Database=DB_C;Trusted_Connection=True;...",
  }
}

3. 在启动时注册：

services.AddDbContext<DBContext_A>(ops =>
{
    ops.UseSqlServer(Configuration.GetConnectionString($"Connection_A"));
});

services.AddDbContext<DBContext_B>(ops =>
{
    ops.UseSqlServer(Configuration.GetConnectionString($"Connection_B"));
});

services.AddDbContext<DBContext_C>(ops =>
{
    ops.UseSqlServer(Configuration.GetConnectionString($"Connection_C"));
});

4. 注入 controller：

public FooController : Controller
{
    private readonly DBContext_A _context_A;
    private readonly DBContext_B _context_B;
    private readonly DBContext_C _context_C;

    public FooController(
            DBContext_A context_A, 
            DBContext_B context_B, 
            DBContext_C context_C)
    {
        _context_A = context_A;
        _context_B = context_B;
        _context_C = context_C;
    }
}

Code First 方法的其他最佳实践：

为每个上下文创建一个 class 库，因此当您应用迁移时，每个上下文将在其自己的项目中拥有自己的迁移文件夹。

• 解决方案
  • 主要项目
    • 启动.cs
  • 类库_A
    • DbContext_A.cs
    • 迁移 // 文件夹
  • 类库_B
    • DbContext_B.cs
    • 迁移 // 文件夹
  • 类库_C
    • DbContext_C.cs
    • 迁移 // 文件夹

在多上下文解决方案中应用迁移时；

• 从解决方案资源管理器中，将主项目（使用 startup.cs）设置为“启动项目”
• 将 package 管理器控制台中的相关 ClassLibrary_A 或 B 或 C 设置为“默认项目”
• 将目标上下文添加到每个 cmd 如下：

PM > add-migration Init -Context DBContext_A
PM > update-database -Context DBContext_A

PM > add-migration Init -Context DBContext_B
PM > update-database -Context DBContext_B

PM > add-migration Init -Context DBContext_C
PM > update-database -Context DBContext_C

或者，您可以使用完整的 PM cmd，如下所示：

PM > add-migration Init -Context DBContext_A -Project ClassLibrary_A -StartupProject MainProject
PM > update-database -Context DBContext_A -Project ClassLibrary_A -StartupProject MainProject

PM > add-migration Init -Context DBContext_B -Project ClassLibrary_B -StartupProject MainProject
PM > update-database -Context DBContext_B -Project ClassLibrary_B -StartupProject MainProject

PM > add-migration Init -Context DBContext_C -Project ClassLibrary_C -StartupProject MainProject
PM > update-database -Context DBContext_C -Project ClassLibrary_C -StartupProject MainProject