EFCore-仅当另一个表中不存在种子数据时 [英] EFCore - Seed data only if it doesn't exist in another table
问题描述
我想在.net core 3.1中使用EntityFramework播种一些数据,并且遇到一个问题:
I want to seed some data using EntityFramework in .net core 3.1 and I'm facing an issue:
我有两个SQL表(所以有两个DbSet< ;>):
I've got two SQL tables (so two DbSet<>):
public virtual DbSet<TableA> TableA { get; set; }
public virtual DbSet<TableB> TableB { get; set; }
表A具有以下结构:
[Key]
public int Id { get; set; } // PK
public string EnglishText { get; set; } // some value
表B具有以下结构:
[Key]
public int Id { get; set; } // PK
public int TableAId { get; set; } // FK to Table A
public string TranslatedText { get; set; } // some value
要为表A播种数据,我使用OnModelCreating(ModelBuilder modelBuilder) DBContext中的方法:
For seeding the data for table A, I use the OnModelCreating(ModelBuilder modelBuilder) method in the DBContext:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
// Seed TableA
modelBuilder.Entity<TableA>().HasData(
new TableA { Id = 1, EnglishText = "first data"}
);
}
我只想在表B不包含记录的情况下播种通过FK引用TableA,我不确定如何在OnModelCreating方法中做到这一点。
I then want to seed table B only if it doesn't contain a record that reference TableA (via the FK), I'm not sure how to do that in the OnModelCreating method.
我想我正在寻找类似的东西:
I guess I'm after something like:
modelBuilder.Entity<TableB>().HasData(var X = new TableB{...}).Where([X.TableAId is not in TableA])
如果有人有想法或可以指出我的方向,那
If someone has an idea or can point me in a direction, that would be very much appreciated.
推荐答案
我遇到了完全相同的问题。所以我决定扩展 DataBuilder
如下:
I had the exact same problem. So i decided to extend DataBuilder
as follow:
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using System;
using System.Collections.Generic;
namespace Infrastructure
{
static class DataBuilderDynamicData
{
private static object asyncObject = new object();
private static Dictionary<Type, List<EntityBase>> dynamicData = new Dictionary<Type, List<EntityBase>>();
public static DataBuilder<TEntity> HasDynamicData<TEntity>(this EntityTypeBuilder<TEntity> builder, Func<Dictionary<Type, List<EntityBase>>, TEntity> Resolver) where TEntity : EntityBase
{
var targetType = typeof(TEntity);
TEntity model;
//Note: Not necessary, but just in case several threads reached the same code scope.
//Note: Lock has some performance hits, but it is negligible due to the fact that Seeding is an In-Design-time process (not run-time).
lock (asyncObject)
{
model = Resolver(dynamicData);
if (dynamicData.ContainsKey(targetType))
dynamicData[targetType].Add(model);
else
dynamicData.Add(targetType, new List<EntityBase> { model });
}
return builder.HasData(model);
}
}
}
然后用它代替 HasData()
像下面的代码:
Then use it instead of HasData()
like following code:
foreach (var model in models)
{
builder.HasDynamicData<ProvinceMap>((dic) =>
{
//Please note that "Province" should be already seeded with "HasDynamicData" method. Otherwise, you get an error here.
var provinces = dic[typeof(Province)];
return new ProvinceMap
{
Id = 1,
ProvinceId = provinces.Cast<Province>().First(item => item.Name=="SOME-PROVINCE"),
//Some other seed data.
};
});
}
请注意, EntityBase
是我的自定义基类。您可以改用 object
。
Please note that EntityBase
is my custom base class. You can use object
instead.
public abstract class EntityBase
{
public int Id { get; set; }
}
每个实体,例如省
和 ProvinceMap
继承自 EntityBase
。
您可以通过将relevent配置代码放在使用者类()之前的方式中,以确保字典已经具有所需的基本数据(在我的示例中:Province类):
Every entities e.g. Province
and ProvinceMap
are inherited from EntityBase
.
You can make sure that dictionary already has the base data you want (in my example: Province class) with placing the relevent config code prior to consumer class ()in my example ProvinceMap class:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.ApplyConfiguration<Province>(new ProvinceConfiguration()); //First, declare the base class.
modelBuilder.ApplyConfiguration<ProvinceMap>(new ProvinceMapConfiguration()); //Next, declare the consumer class.
}
您可以实现 HasData()$ c的其他重载$ c>方法来满足您的需求。
You can implement other overloads of the HasData()
method to fit your needs.
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