全局禁用EF Core 2上的级联删除

Question

我需要了解全局禁用EF Core 2中级联删除的方法。感谢您的帮助。

在EF 6. x中，我们使用以下代码来禁用OneTo多和ManyTo多实现上的级联删除：

builder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
builder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();

Answer 1

可能有帮助：

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
ChangeTracker.CascadeDeleteTiming = ChangeTracking.CascadeTiming.Never;
ChangeTracker.DeleteOrphansTiming = ChangeTracking.CascadeTiming.Never;
}

Answer 2

constraints: table =>
                {
                    table.PrimaryKey("PK_ComandaPlato", x => x.ComandaPlatoId);
                    table.ForeignKey(
                        name: "FK_ComandaPlato_Comanda_ComandaId",
                        column: x => x.ComandaId,
                        principalTable: "Comanda",
                        principalColumn: "ComandaId",
                        onDelete: ReferentialAction.Cascade);//default: cascade on
                    table.ForeignKey(
                        name: "FK_ComandaPlato_Plato_PlatoId",
                        column: x => x.PlatoId,
                        principalTable: "Plato",
                        principalColumn: "PlatoId",
                        onDelete: ReferentialAction.NoAction);//turn off cascade,"by hand"
                });
//comments: modifing the auto-generated migration, "harcode by hand" this attibute, as view bellow: change "Cascade" to "NoAction" (as view 1st and 2st examples)

Answer 3

不幸的是，EF Core目前（最新版本为v2.0）并没有提供一种在全球范围内控制这些约定的好方法。

默认的EF Core 2.0约定是使用DeleteBePerformance or。Cascade用于必需和DeleteBeAct or。ClientSetNull用于可选关系。我可以建议作为解决方法的是OnModelCreating覆盖末尾的典型元数据模型循环。在这种情况下，定位所有已经发现的关系并相应地修改它们：

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    // ...

    var cascadeFKs = modelBuilder.Model.GetEntityTypes()
        .SelectMany(t => t.GetForeignKeys())
        .Where(fk => !fk.IsOwnership && fk.DeleteBehavior == DeleteBehavior.Cascade);

    foreach (var fk in cascadeFKs)
        fk.DeleteBehavior = DeleteBehavior.Restrict;

    base.OnModelCreating(modelBuilder);
}