EF6 - 无种子运行Update-Database命令 [英] EF6 - Run Update-Database Command without seeds
问题描述
我正在使用实体框架6,我正在使用迁移。我已经使用初始迁移创建了数据库。现在我已经对模型做了修改,并且上下文已经改变了,我想要更新数据库BUT ...
当我再次尝试运行数据库更新
命令种子也在运行,这会导致错误,因为一些数据被再次插入。
I'm Using Entity Framework 6 and I'm using migrations. I have already created the database using an initial migration. Now I have done changes to the Model and the context has changed, and I want to update the database BUT...
When I try to run again the Database-Update
command the seeds are also running too, and this bring errores due some data is inserted again.
很难相信EF没有任何简单的选项,如 -No-Seed
。
It is hard to believe that EF doesn't have any simple option like -No-Seed
for that. I'm almost secure that other ORMs does.
推荐答案
从源代码 DbMigrationsConfiguration< TContext>
:
/// <summary>
/// Runs after upgrading to the latest migration to allow seed data to be updated.
///
/// </summary>
///
/// <remarks>
/// Note that the database may already contain seed data when this method runs. This means that
/// implementations of this method must check whether or not seed data is present and/or up-to-date
/// and then only make changes if necessary and in a non-destructive way. The
/// <see cref="M:System.Data.Entity.Migrations.DbSetMigrationsExtensions.AddOrUpdate``1(System.Data.Entity.IDbSet{``0},``0[])"/>
/// can be used to help with this, but for seeding large amounts of data it may be necessary to do less
/// granular checks if performance is an issue.
/// If the <see cref="T:System.Data.Entity.MigrateDatabaseToLatestVersion`2"/> database
/// initializer is being used, then this method will be called each time that the initializer runs.
/// If one of the <see cref="T:System.Data.Entity.DropCreateDatabaseAlways`1"/>, <see cref="T:System.Data.Entity.DropCreateDatabaseIfModelChanges`1"/>,
/// or <see cref="T:System.Data.Entity.CreateDatabaseIfNotExists`1"/> initializers is being used, then this method will not be
/// called and the Seed method defined in the initializer should be used instead.
///
/// </remarks>
/// <param name="context">Context to be used for updating seed data. </param>
基本上,您没有其他选项来实现添加或更新逻辑,因为种子方法将在使用初始化程序后每次执行。
Basically, you don't have another option than implement an "add or update" logic because the Seed method will be executed each time after the initializer is used.
AddOrUpdate扩展方法对此有用,但在某些情况下,我也使用过:
The AddOrUpdate extension method is useful for this, but I have also used this in some cases:
if (!context.Entities.Any())
{
// Seed
}
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