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。

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()
    {
    }
}

在EF6

删除“migrations”文件夹中的所有文件…但不是'初始创建'或'配置'。 删除数据库。 现在运行Add-Migration Initial。 现在你可以“update-database”，一切都会好起来。

在EntityFramework 6中，请尝试:

Add-Migration Initial

以便更新初始迁移文件。

VSC(Visual Studio Code) - .Net核心

1.删除状态:删除项目中的迁移文件夹;

2.删除数据库中__MigrationHistory的记录;

3.Dotnet ef数据库drop -v then 您确定要删除服务器上的数据库'<your-database' ?(y / N) 写“N”

4.. dotnet ef迁移添加Initial，然后将20211014110429_initial类的代码写入__MigrationHistory的

Enable-Migrations -EnableAutomaticMigrations -Force