生成迁移ef核心的访问方法

Question

无论如何，当您在Entity Framework Core中调用Add-Migration时，是否可以访问用于创建数据库迁移的方法？

如果这有所不同，则它在.NET Core 2.2项目中。

Answer 1

要访问Migration，可以实现MigrationsAssembly。

1. 实施ColumnOrderMigrationAssembly

   public class ColumnOrderMigrationAssembly : MigrationsAssembly
   {
       private readonly DbContext _context;
   
       public ColumnOrderMigrationAssembly(ICurrentDbContext currentContext,
           IDbContextOptions options, IMigrationsIdGenerator idGenerator,
           IDiagnosticsLogger<DbLoggerCategory.Migrations> logger)
       : base(currentContext, options, idGenerator, logger)
       {
           _context = currentContext.Context;
       }
   
       public override Migration CreateMigration(TypeInfo migrationClass,
           string activeProvider)
       {
           var migration = base.CreateMigration(migrationClass, activeProvider);
           var productTableMigration = migration.UpOperations.FirstOrDefault(m => m.GetType() == typeof(CreateTableOperation) 
           && ((CreateTableOperation)m).Name == "Products") as CreateTableOperation;
           if (productTableMigration != null)
           {
               var columns =new List<AddColumnOperation>(productTableMigration.Columns.OrderBy(o => o.Name));
               productTableMigration.Columns.Clear();
               productTableMigration.Columns.AddRange(columns);
           }
           return migration;
       }
   }
   

2. 注册ColumnOrderMigrationAssembly

   services.AddDbContext<ApplicationDbContext>(options =>
       options.UseSqlServer(
           Configuration.GetConnectionString("DefaultConnection"))
           .ReplaceService<IMigrationsAssembly, ColumnOrderMigrationAssembly>());
   

3. 启用migrate

   public void Configure(IApplicationBuilder app, IHostingEnvironment env, IServiceProvider serviceProvider)
   {
       //your rest code
       using (var db = serviceProvider.CreateScope().ServiceProvider.GetRequiredService<ApplicationDbContext>())
       {
           db.Database.Migrate();
       }
   }
   

   根据自己的需要更改CreateMigration中的逻辑。

Answer 2

在运行Add-Migration的项目下，有一个名为Migration的文件夹，在其中添加了Migration类。重新运行迁移时，您可以更改列的顺序。