...可能会导致循环或多个级联路径。指定ON DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他FOREIGN KEY约束

Question

Entity Framework核心

更新数据库时抛出错误

错误：- 在 table 'UserRoleRelationship' 上引入 FOREIGN KEY 约束 'FK_UserRoleRelationship_UserRoels_ParentUserRoleId' 可能会导致循环或多个级联路径。指定 ON DELETE NO ACTION 或 ON UPDATE NO ACTION，或修改其他 FOREIGN KEY 约束。 无法创建约束或索引。

public class UserRoleRelationship 
{
    [Key]
    public int Id { get; set; }
    [Required]
    public Guid UserRoleRelationshipId { get; set; }

    public virtual UserRole ChildUserRole { get; set; }
    public int ChildUserRoleId { get; set; }

    public virtual UserRole ParentUserRole { get; set; }
    public int ParentUserRoleId { get; set; }

}

public class UserRole 
{
    [Key]
    public int Id { get; set; }
    [Required]
    public Guid UserRoleId { get; set; }
    public virtual Role Role { set; get; }
    public int RoleId { set; get; }
    public virtual U.User User { set; get; }
    public int UserId { set; get; }
}

Answer 1

对于您当前的模型设计，它将在下面创建迁移：

            migrationBuilder.AddForeignKey(
            name: "FK_UserRoleRelationship_UserRole_ChildUserRoleId",
            table: "UserRoleRelationship",
            column: "ChildUserRoleId",
            principalTable: "UserRole",
            principalColumn: "Id",
            onDelete: ReferentialAction.Cascade);

        migrationBuilder.AddForeignKey(
            name: "FK_UserRoleRelationship_UserRole_ParentUserRoleId",
            table: "UserRoleRelationship",
            column: "ParentUserRoleId",
            principalTable: "UserRole",
            principalColumn: "Id",
            onDelete: ReferentialAction.Cascade);

FK_UserRoleRelationship_UserRole_ChildUserRoleId和FK_UserRoleRelationship_UserRole_ParentUserRoleId在删除UserRoleRelationship时都会删除UserRole中的记录，会造成多次级联删除。

对于解决方法，请尝试将 int 设为 int?，如下所示：

        public int? ParentUserRoleId { get; set; }

这将创建

migrationBuilder.AddForeignKey(
                name: "FK_UserRoleRelationship_UserRole_ParentUserRoleId",
                table: "UserRoleRelationship",
                column: "ParentUserRoleId",
                principalTable: "UserRole",
                principalColumn: "Id",
                onDelete: ReferentialAction.Restrict);

备注
您需要先删除UserRole，然后再删除UserRoleRelationship

Answer 2

解决方法是，尝试将 int 设为 int?，如下所示：

public int? ParentUserRoleId { get; set; }