在EF4.1中如何仅在创建数据库时创建索引？
我正在使用 EF4.1 CodeFirst 创建模型。我使用：
Database.SetInitializer(Of dbModel.dbDB2Data)(New DropCreateDatabaseIfModelChanges(Of dbModel.dbDB2Data))
并
MyBase.Database.ExecuteSqlCommand("CREATE INDEX IX_EXPLAN ON DBO.EXPLANS (PROGNAME, BIND_TIME, ACCESSNAME)")
创建索引。问题是，如果我将 ExecuteSqlCommand 放在 DbContext New 子例程中，则每次启动应用程序时它都会执行，即使数据库已经存在，然后会发生错误，因为索引已经存在。如果我将它放在 OnModelCreating 事件中，则会收到以下错误：
The context cannot be used while the model is being created.
那么如何让 ExecuteSqlCommand 仅在创建数据库时执行其操作？
I am creating a model with EF4.1 CodeFirst. I use:
Database.SetInitializer(Of dbModel.dbDB2Data)(New DropCreateDatabaseIfModelChanges(Of dbModel.dbDB2Data))
And
MyBase.Database.ExecuteSqlCommand("CREATE INDEX IX_EXPLAN ON DBO.EXPLANS (PROGNAME, BIND_TIME, ACCESSNAME)")
to create an index. The problem is, if I put the ExecuteSqlCommand in the DbContext New subroutine, it executes everytime the application is started, even if the DB already exists, and then an error occures because the index already exists. If I put it in the OnModelCreating event, I get the following error:
The context cannot be used while the model is being created.
So how can I have the ExecuteSqlCommand do its thing only when the DB is being created?
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您需要创建自定义数据库初始值设定项并在初始值设定项的 Seed 方法中执行 SQL 命令。初始化程序仅在创建数据库时调用一次。 这里是具有唯一索引的类似示例。
You need to create custom database initializer and execute your SQL command in the Seed method of the initializer. The initializer is called only once when the database is created. Here is similar example with unique index.