Question

我正在为.NET Core应用程序开发一个可重用的小型程序包，该程序包将有助于在应用程序启动时自动迁移。

它基本上将在每个DbContext上运行Database.Migrate()。

但是这里的事情是，我只想在已经“标记”为自动迁移的DbContexts上运行它。我以为我可以扩展AddDbContext，并以某种方式告诉IServiceCollection来跟踪特定的DbContext。像这样：

public static IServiceCollection AddDbContextWithMigration<TContext>(this IServiceCollection serviceCollection, Action<DbContextOptionsBuilder> optionsAction = null, ServiceLifetime contextLifetime = ServiceLifetime.Scoped, ServiceLifetime optionsLifetime = ServiceLifetime.Scoped) where TContext : DbContext
{
    //TODO: Somehow remember that this DbContext should be migrated.
    return serviceCollection.AddDbContext<TContext, TContext>(optionsAction, contextLifetime, optionsLifetime);
}

用法：

public IServiceProvider ConfigureServices(IServiceCollection services)
{
    services.AddDbContextWithMigration<DbContext1>();
    services.AddDbContext<DbContext2>();
    services.AddDbContextWithMigration<DbContext3>();
}

然后我认为我可以使用IStartupFilter或为IApplicationBuilder创建扩展方法。

使用扩展方法：

public static IApplicationBuilder RunMigrations(this IApplicationBuilder app)
{
    if (app == null)
        throw new ArgumentNullException(nameof(app));

    var contexts = app.ApplicationServices.GetService();
    foreach (DbContext context in contexts)
    {
        context.Database.Migrate();
    }

    return app;
}

使用IStartupFilter：

public class MigrationsFilter : IStartupFilter
{
    public Action<IApplicationBuilder> Configure(Action<IApplicationBuilder> next)
    {
        return builder =>
        {
            var contexts = builder.ApplicationServices.GetService();
            foreach (DbContext context in contexts)
            {
                context.Database.Migrate();
            }

            next(builder);
        };
    }
}

所以我基本上有两个问题。

如何跟踪应该迁移哪些DbContext？
这是IStartupFilter的“正确”用法吗？

Answer 1

我为迁移注册了包装类（IContextMigrator）。

首先，我的扩展方法：

public static IApplicationBuilder RunMigrations(this IApplicationBuilder app)
{
    if (app == null)
        throw new ArgumentNullException(nameof(app));


    IEnumerable<IContextMigrator> migrations = app.ApplicationServices.GetServices<IContextMigrator>();

    foreach (IContextMigrator migration in migrations)
    {
        migration.Migrate();
        // Other logic for dispose...
    }

    return app;
}


public static IServiceCollection AddDbContextWithMigration<TContext>(this IServiceCollection serviceCollection, Action<DbContextOptionsBuilder> optionsAction = null, ServiceLifetime contextLifetime = ServiceLifetime.Scoped, ServiceLifetime optionsLifetime = ServiceLifetime.Scoped) where TContext : DbContext
{
    // By simply registering a transient of a wrapper-class I can resolve it later.
    serviceCollection.AddTransient<IContextMigrator, ContextMigrator<TContext>>();
    return serviceCollection.AddDbContext<TContext, TContext>(optionsAction, contextLifetime, optionsLifetime);
}

然后我的班级进行实际迁移：

public interface IContextMigrator : IDisposable
{
    void Migrate();
}

/// <summary>
/// Class responsible for migration of a DbContext.
/// Used by ApplicationBuilderExtensions to perform migrations.
/// </summary>
/// <typeparam name="T"></typeparam>
internal sealed class ContextMigrator<T> : IContextMigrator
    where T : DbContext
{
    private readonly T context;

    public ContextMigrator(T context)
    {
        this.context = context;
    }

    public void Migrate()
    {
        try
        {
            this.context.Database.Migrate();
        }
        catch (Exception e)
        {
            throw new MigrationException(context.GetType().Name, e);
        }
    }

    public void Dispose()
    {

    }
}

选择要在启动时自动迁移的DbContext

1 个答案: