如何使用DbContext處理多源資料庫

我使用了干凈的拱形步驟來創建專案，但問題是我有超過三個聚合，我需要將它們放入參考資料庫中。

我嘗試為每個聚合使用 DbContext，如下所示：

public class AppDbContext : DbContext
{
  private readonly IMediator? _mediator;

  public AppDbContext(DbContextOptions<AppDbContext> options, IMediator? mediator)
      : base(options)
  {
    _mediator = mediator;
  }
.
.
.
public class AnalyzeDbContext : DbContext
{
  private readonly IMediator? _mediator;

  public AnalyzeDbContext(DbContextOptions<AnalyzeDbContext> options, IMediator? mediator)
      : base(options)
  {
    _mediator = mediator;
  }
.
.
.
public class ProviderMgrDbContext : DbContext
{
  private readonly IMediator? _mediator;


  public ProviderMgrDbContext(DbContextOptions<ProviderMgrDbContext> options, IMediator? mediator)
      : base(options)
  {
    _mediator = mediator;
  }

我為每個 DbContext 發送連接字串，如下所示：

//#Update 1
 public static void AppDbContext(this IServiceCollection services, string connectionString) =>
   services.AddDbContext<AppDbContext>(options => options.UseMySQL(connectionString));

 public static void ProviderMgrDbContext(this IServiceCollection services, string connectionString) =>
   services.AddDbContext<ProviderMgrDbContext>(options => options.UseMySQL(connectionString));

  public static void AnalyzeDbContext(this IServiceCollection services, string connectionString) =>
   services.AddDbContext<AnalyzeDbContext>(options => options.UseMySQL(connectionString));

//#After
public static void AppDbContext(this IServiceCollection services, string connectionString) =>
   services.AddDbContext<AppDbContext>(options => options.UseMySql(connectionString, new MySqlServerVersion(new Version(8, 0, 27))));

 public static void ProviderMgrDbContext(this IServiceCollection services, string connectionString) =>
   services.AddDbContext<ProviderMgrDbContext>(options => options.UseMySql(connectionString, new MySqlServerVersion(new Version(8, 0, 27))));
  
  public static void AnalyzeDbContext(this IServiceCollection services, string connectionString) =>
   services.AddDbContext<AnalyzeDbContext>(options => options.UseMySql(connectionString, new MySqlServerVersion(new Version(8, 0, 27))));
.
.
.

但是當我嘗試遷移它們時，它會顯示如下豁免錯誤：

PM> Add-Migration init_1 -context AppDbContext
Build started...
Build succeeded.
Autofac.Core.DependencyResolutionException: An exception was thrown while activating WetaPayment.Infrastructure.Data.DataContext.AppDbContext.
 ---> Autofac.Core.DependencyResolutionException: An exception was thrown while invoking the constructor 'Void .ctor(Microsoft.EntityFrameworkCore.DbContextOptions`1[WetaPayment.Infrastructure.Data.DataContext.AppDbContext], MediatR.IMediator)' on type 'AppDbContext'.
 ---> System.TypeLoadException: Method 'AppendIdentityWhereCondition' in type 'MySql.EntityFrameworkCore.MySQLUpdateSqlGenerator' from assembly 'MySql.EntityFrameworkCore, Version=5.0.8.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d' does not have an implementation.

最后我修復了MySql.EntityFrameworkCore與 net6.0 不兼容的更改包的部分問題，所以我使用了Pomelo.EntityFrameworkCore.MySql它并且它成功地作業。

但是我仍然有另一個問題，即我的所有聚合在所有背景關系中都禿了，我需要每個 DbContext 只構建他的聚合，那么如何修復它？

uj5u.com熱心網友回復：

每個人都DbContext可以配置自己的物體

假設我們有 10 個物體 3 DbContext，我們可以將它們分成 2 個物體ADbContext，5個物體BDbContext和 3個物體CDbContext。FK明智地管理它們之間的配置，否則，那將變得混亂。這是使用 fluent API 執行此操作的方法

public class MyAppDbContext : DbContext
{
    public DbSet<OurEntity> OurEntity { get; set; }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.Entity<OurEntity>(builder => 
       {
            // Our implementation goes here...
       });
    }
}

像那樣，我們只配置和注冊與每個DbContext.

我們需要將每個DbContext單獨注冊到任何型別的 DI

為每個組織遷移操作 DbContext

我通常將它們組織在這樣的檔案夾中：

Data/Migrations/ContextA
Data/Migrations/ContextB
Data/Migrations/ContextC

每個背景關系都有自己的遷移和快照。

通過DbContext在使用EF遷移工具時單獨指定來執行此操作

add-migration add [MigrationName] -context [DbContextName] -o [Path to desire place to store migration]

然后分別應用它們

update-database -context [DbContextName]

標籤：C＃ 实体框架 asp.net核心 领域驱动设计 ardalis-cleanarchitecture

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