根据Customizing the Migrations History Table,我应该能够添加一列,但是我无法找到有关如何实际添加新列的任何示例。
我很担心放置实际属性的位置以及如何将其配置到现有的__MigrationHistory表。从文档中,我可以自定义表配置..
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<HistoryRow>().ToTable(tableName: "MigrationHistory", schemaName: "admin");
modelBuilder.Entity<HistoryRow>().Property(p => p.MigrationId).HasColumnName("Migration_ID");
}
...但我无法修改HistoryRow
实体。
我是否应该根据HistoryRow
实体添加新的派生类型?
答案 0 :(得分:7)
首先,您需要为历史记录行实体创建一个新类。例如:
public sealed class MyHistoryRow : HistoryRow
{
//We will just add a text column
public string MyColumn { get; set; }
}
接下来我们需要一个上下文,就像我们对普通EF操作一样,但这次我们继承自HistoryContext
:
public class MyHistoryContext : HistoryContext
{
//We have to 'new' this as we are overriding the DbSet type
public new DbSet<MyHistoryRow> History { get; set; }
public MyHistoryContext(DbConnection dbConnection, string defaultSchema)
: base(dbConnection, defaultSchema)
{
}
//This part isn't needed but shows what you can do
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
//Rename the table and put it in a different schema. Our new table
//will be called 'admin.MigrationHistory'
modelBuilder.Entity<MyHistoryRow>().ToTable(tableName: "MigrationHistory", schemaName: "admin");
//Rename one of the columns for fun
modelBuilder.Entity<MyHistoryRow>().Property(p => p.MigrationId).HasColumnName("Migration_ID");
}
}
现在要连接它们,我们需要配置它,所以首先我们设置配置:
public class MyConfiguration : DbConfiguration
{
public MyConfiguration()
{
//Set our new history context to be the one that gets used
this.SetHistoryContext("System.Data.SqlClient",
(connection, defaultSchema) => new MyHistoryContext(connection, defaultSchema));
}
}
最后,通过修改我们的web.config来使配置适用:(你必须填写你自己的命名空间和应用程序集:
<entityFramework codeConfigurationType="Namespace.MyConfiguration, ApplicationAssembly">
...snipped...
</entityFramework>
执行此操作的副作用是,如果/当您启用迁移时,您需要明确说明您正在使用的上下文。这显然是因为你现在在程序集中有两种上下文类型(除非你将它们拆分出来。)所以你现在需要运行这样的命令:
enable-migrations -ContextTypeName Namespace.YourContextClass