Enable-Migrations -EnableAutomaticMigrations -Force

这个方法不需要删除__MigrationHistory表，所以你不必在部署时把你的手放在数据库上。

从migrations文件夹中删除现有的迁移。 在包管理控制台运行Add-Migration ResetMigrations 清理Up()方法中的迁移历史:

/// <summary>
/// Reset existing migrations by cleaning the __MigrationHistory table
/// and creating a new initial migration with the current model snapshot.
/// </summary>
public partial class ResetMigrations : DbMigration
{
    public override void Up()
    {
        Sql("DELETE FROM [dbo].[__MigrationHistory]");
    }

    public override void Down()
    {
    }
}

问题:你搞砸了你的迁移，你想重置它而不删除现有的表。

问题:您不能重置数据库中现有表的迁移，因为EF希望从头创建表。

应对方法:

Delete existing migrations from Migrations_History table. Delete existing migrations from the Migrations Folder. Run add-migration Reset. This will create a migration in your Migration folder that includes creating the tables (but it will not run it so it will not error out.) You now need to create the initial row in the MigrationHistory table so EF has a snapshot of the current state. EF will do this if you apply a migration. However, you can't apply the migration that you just made as the tables already exist in your database. So go into the Migration and comment out all the code inside the "Up" method. Now run update-database. It will apply the Migration (while not actually changing the database) and create a snapshot row in MigrationHistory.

现在您已经重置了迁移，可以继续进行正常的迁移。

考虑到当我们在。net Core中搜索EF时仍然会出现这个问题，我将在这里发布我的答案(因为它一直困扰着我)。注意，EF 6 .NET版本有一些微妙之处(没有初始命令，你将需要删除“快照”文件)

(在。net Core 2.1中测试)

以下是步骤:

删除_efmigrationhistory表。 在整个解决方案中搜索名称中包含Snapshot的文件，例如ApplicationDbContextSnapshot.cs，然后删除它们。 重新构建解决方案 执行Add-Migration InitialMigration命令

请注意: 必须删除所有快照文件。我花了无数个小时删除数据库……如果您不这样做，这将生成一个空迁移。

此外，在#3中，您可以随意命名您的迁移。

以下是一些额外的资源: asp.net CORE迁移生成空

重置实体框架7迁移

删除迁移文件夹，清理然后重建项目。这对我很管用。在清理和重建之前，它说迁移已经存在，因为在它的缓存内存中，它还没有删除。

对于 EFCore 6/7：

为了将所有更改合并到单个文件中，并将其应用到现有数据库中，同时保留所有数据(即在Production和其他开发中)，以下步骤对我来说很有效:

Delete existing migrations from the Migrations Folder in your project. Delete the Context Snapshop files. I.e. ApplicationDbContextSnapshot.cs, DatabaseContextModelSnapshot.cs or similar. Rebuild your solution Run Add-Migration Initial. (Can be named how you like instead of Initial). This will create a migration in your Migration folder that includes creating the tables, but won't be applied yet. Open the generated Migration file and comment out all the code inside the "Up" method, so that it doesn't make any changes to all your existing tables. (This allows us to update the database in the correct format, without making any changes in the next step) Before the commented code within the Up function, add migrationBuilder.Sql("DELETE FROM [dbo].[__EFMigrationsHistory]"); to have the delete/truncate applied during migration

public partial class Initial : Migration
{
    public override void Up()
    {
        migrationBuilder.Sql("DELETE FROM [dbo].[__EFMigrationsHistory]");
        /*
          OTHER COMMENTED OUT CODE
        */
    }

    public override void Down()
    {
    }
}

Run Update-Database. It will apply the Migration and remove existing migration tracking entriers (while not actually changing the database schema) and create a snapshot row in __EFMigrationsHistory Submit this code and apply to your dev, staging and production databases as you normally would (Ensure the code is still commented out in the Up function, no changes will be applied, except a new entry created in __EFMigrationsHistory) Remove migrationBuilder.Sql("DELETE FROM [dbo].[__EFMigrationsHistory]"); and uncomment all the code from step 5 and submit back to source control. (This way new devs can create the db from scratch. If someone forgot to update their existing database, it'll error out and complain that the tables already exist, so they can just comment the Initial file out and apply.)