entity-framework-core - EF Core - 如何在没有级联删除的情况下配置所需的外键

Question

我在一件很简单的事情上遇到了麻烦。 ( Entity Framework 核心 5)
我为派生了几个子类的基本模型编写了以下配置类。
楷模:

abstract public class RecordBase
{
    public Guid Id { get; set; }
}

public class Item : RecordBase
{
    public string name { get; set; }
}

[NotMapped]
public abstract class LineBase : RecordBase
{
    public Guid ItemId { get; set; }
    public Item Item { get; set; }
    public string Unit { get; set; }
    public double Qty { get; set; }
    public virtual ICollection<ItemTransaction> ItemTransactions { get; set; } = new Collection<ItemTransaction>();
    public virtual ProductDim ProductDim { get; set; } 
}

public abstract class OrderLineBase : LineBase
{
    public string OrderNum { get; set; }
}

public abstract class JournalLineBase : LineBase
{
    public string JournalNum { get; set; }
}

public class SalesOrderLine : OrderLineBase
{
    public string CustomerNum { get; set; }
}

public class PurchOrderLine : OrderLineBase
{
    public string CustomerNum { get; set; }
}

public class WmsJournalLine : JournalLineBase
{
    public string Warehouse { get; set; }
}

public class ItemTransaction : RecordBase
{
    public DateTime TransDateTime { get; set; }
    public virtual LineBase Line { get; set; }
    public string Reference{ get; set; }
}

public class ProductDim : RecordBase
{
    public int Configuration { get; set; }
    public virtual ICollection<LineBase> LineBases { get; set; }
}

所以我正在定义与 ProductDim Table 的关系，它不能为空。
所以我建立了关系使它 IsRequired()并设置 DeleteBehavior至 Restrict .

class LineBaseConfiguration<TEntity> : IEntityTypeConfiguration<TEntity>
    where TEntity : LineBase
{
    public virtual void Configure(EntityTypeBuilder<TEntity> modelBuilder)
    {        
        modelBuilder.HasOne(x => x.ProductDim)
                    .WithMany(x => (ICollection<TEntity>)x.LineBases)
                    .HasForeignKey("ProductDimId")
                    .IsRequired()
                    .OnDelete(DeleteBehavior.Restrict);       
    }
}

该配置将应用于我的 LineBase 的子模型模型:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);
    ...
    modelBuilder.ApplyConfiguration<SalesOrderLine>(new LineBaseConfiguration<SalesOrderLine>());
    modelBuilder.ApplyConfiguration<WmsJournalLine>(new LineBaseConfiguration<WmsJournalLine>());
    modelBuilder.ApplyConfiguration<PurchOrderLine>(new LineBaseConfiguration<PurchOrderLine>());
    ...
}

现在，当我将迁移添加到我的项目时，外键生成为 ReferentialAction.Cascade .
迁移输出:

migrationBuilder.AddForeignKey(
    name: "FK_PurchOrderLine_ProductDim_ProductDimId",
    table: "PurchOrderLine",
    column: "ProductDimId",
    principalTable: "ProductDim",
    principalColumn: "Id",
    onDelete: ReferentialAction.Cascade);

migrationBuilder.AddForeignKey(
    name: "FK_SalesOrderLine_ProductDim_ProductDimId",
    table: "SalesOrderLine",
    column: "ProductDimId",
    principalTable: "ProductDim",
    principalColumn: "Id",
    onDelete: ReferentialAction.Cascade);

migrationBuilder.AddForeignKey(
    name: "FK_WmsJournalLine_ProductDim_ProductDimId",
    table: "WmsJournalLine",
    column: "ProductDimId",
    principalTable: "ProductDim",
    principalColumn: "Id",
    onDelete: ReferentialAction.Cascade);

仅当我删除 IsRequired()从我的模型配置。生成正确的RefrentialAction。但是后来我使外键属性可以为空，这是我必须避免的。
在这种情况下，迁移会生成多个级联路径。所以它是无用的，因为我不能将它应用到我的数据库中。
那么有没有其他方法可以让我的 ForeignKey 字段成为不可为空且正确的删除操作？

Answer 1

我不知道为什么，但是 IsRequired在实体中添加外键。对外键构建器(如 OnDelete )所做的所有修改都不会影响外键，因为它已经构建并添加到实体中。这听起来像一个错误。
解决方案(hack？)是调用 IsRequired终于 :

modelBuilder.HasOne(x => x.ProductDim)
            .WithMany(x => (ICollection<TEntity>)x.LineBases)
            .HasForeignKey("ProductDimId")
            .OnDelete(DeleteBehavior.Restrict)
            .IsRequired(); // At last