无法更新数据库，因为实体无法删除约束

我创建了一些新表，我注意到我没有为id使用良好的命名约定。

所以我用新的id做了一个新的add-migration，但是当我尝试update-database时，我有以下错误:

约束'PK_dbo.DB_User_Type'正在被表引用'AspNetUsers'，外键约束"FK_dbo.AspNetUsers_dbo.DB_User_Type_DB_User_Type_Id"。不能掉下来约束。见前面的错误。

我不明白，因为脚本开始删除所有的约束。

有人能解释一下如何解决这个错误吗?

我使用实体6.1的新方法code first from an existing database。下面是Up函数

public override void Up()
        {
            DropForeignKey("dbo.DB_Company_Profile", "DB_Category_Id", "dbo.DB_Category");
            DropForeignKey("dbo.DB_Category_Translation", "DB_Category_Id", "dbo.DB_Category");
            DropForeignKey("dbo.DB_User_Type_Translation", "DB_User_Type_Id", "dbo.DB_User_Type");
            DropForeignKey("dbo.DB_Company_Profile", "category_id", "dbo.DB_Category");
            DropForeignKey("dbo.DB_Category_Translation", "category_id", "dbo.DB_Category");
            DropForeignKey("dbo.AspNetUsers", "DB_User_Type_user_type_id", "dbo.DB_User_Type");
            DropForeignKey("dbo.DB_User_Type_Translation", "user_type_id", "dbo.DB_User_Type");
            DropIndex("dbo.DB_Company_Profile", new[] { "DB_Category_Id" });
            DropIndex("dbo.DB_Category_Translation", new[] { "DB_Category_Id" });
            DropIndex("dbo.DB_User_Type_Translation", new[] { "DB_User_Type_Id" });
            DropColumn("dbo.DB_Company_Profile", "category_id");
            DropColumn("dbo.DB_Category_Translation", "category_id");
            DropColumn("dbo.DB_User_Type_Translation", "user_type_id");
            RenameColumn(table: "dbo.AspNetUsers", name: "DB_User_Type_Id", newName: "DB_User_Type_user_type_id");
            RenameColumn(table: "dbo.DB_Company_Profile", name: "DB_Category_Id", newName: "category_id");
            RenameColumn(table: "dbo.DB_Category_Translation", name: "DB_Category_Id", newName: "category_id");
            RenameColumn(table: "dbo.DB_User_Type_Translation", name: "DB_User_Type_Id", newName: "user_type_id");
            RenameIndex(table: "dbo.AspNetUsers", name: "IX_DB_User_Type_Id", newName: "IX_DB_User_Type_user_type_id");
            DropPrimaryKey("dbo.DB_Category");
            DropPrimaryKey("dbo.DB_User_Type");
            AddColumn("dbo.DB_Category", "category_id", c => c.Int(nullable: false, identity: true));
            AddColumn("dbo.DB_User_Type", "user_type_id", c => c.Int(nullable: false, identity: true));
            AlterColumn("dbo.DB_Company_Profile", "category_id", c => c.Int(nullable: false));
            AlterColumn("dbo.DB_Category_Translation", "category_id", c => c.Int(nullable: false));
            AlterColumn("dbo.DB_User_Type_Translation", "user_type_id", c => c.Int(nullable: false));
            AddPrimaryKey("dbo.DB_Category", "category_id");
            AddPrimaryKey("dbo.DB_User_Type", "user_type_id");
            CreateIndex("dbo.DB_Company_Profile", "category_id");
            CreateIndex("dbo.DB_Category_Translation", "category_id");
            CreateIndex("dbo.DB_User_Type_Translation", "user_type_id");
            AddForeignKey("dbo.DB_Company_Profile", "category_id", "dbo.DB_Category", "category_id", cascadeDelete: true);
            AddForeignKey("dbo.DB_Category_Translation", "category_id", "dbo.DB_Category", "category_id", cascadeDelete: true);
            AddForeignKey("dbo.DB_User_Type_Translation", "user_type_id", "dbo.DB_User_Type", "user_type_id", cascadeDelete: true);
            AddForeignKey("dbo.AspNetUsers", "DB_User_Type_user_type_id", "dbo.DB_User_Type", "user_type_id");
            DropColumn("dbo.DB_Category", "Id");
            DropColumn("dbo.DB_User_Type", "Id");
        }