EF Core - 如何通过一对多关系自引用 model？

Question

我正在尝试使用 ASP.NET 核心身份开发一个基本的推荐系统，其中一个用户可以被另一个用户推荐，也可以引用用户。

会员用户实体：

public class MemberUser : IdentityUser
{
    [Required]
    [MaxLength(100)]
    public string FirstName { get; set; } = string.Empty;

    [Required]
    [MaxLength(100)]
    public string LastName { get; set; } = string.Empty;

    public string? ReferrerId { get; set; }
    public virtual MemberUser Referrer { get; set; }
    public virtual List<MemberUser> Referrals { get; set; }

}

数据库上下文：

protected override void OnModelCreating(ModelBuilder builder)
{
    base.OnModelCreating(builder);
    builder.Entity<MemberUser>()
        .HasOne(mu => mu.Referrer)
        .WithMany(mu => mu.Referrals)
        .HasForeignKey(mu => mu.ReferrerId)
        .OnDelete(DeleteBehavior.NoAction);

}

当我运行 dotnet ef database update 时，它会产生一个错误：

在表“AspNetUsers”上引入 FOREIGN KEY 约束“FK_AspNetUsers_AspNetUsers_ReferrerId”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。 请参阅以前的错误。

protected override void Up(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.CreateTable(
            name: "AspNetRoles",
            columns: table => new
            {
                Id = table.Column<string>(type: "nvarchar(450)", nullable: false),
                Name = table.Column<string>(type: "nvarchar(256)", maxLength: 256, nullable: true),
                NormalizedName = table.Column<string>(type: "nvarchar(256)", maxLength: 256, nullable: true),
                ConcurrencyStamp = table.Column<string>(type: "nvarchar(max)", nullable: true)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_AspNetRoles", x => x.Id);
            });

        migrationBuilder.CreateTable(
            name: "AspNetUsers",
            columns: table => new
            {
                Id = table.Column<string>(type: "nvarchar(450)", nullable: false),
                FirstName = table.Column<string>(type: "nvarchar(100)", maxLength: 100, nullable: false),
                LastName = table.Column<string>(type: "nvarchar(100)", maxLength: 100, nullable: false),
                ReferrerId = table.Column<string>(type: "nvarchar(450)", nullable: false),
                UserName = table.Column<string>(type: "nvarchar(256)", maxLength: 256, nullable: true),
                NormalizedUserName = table.Column<string>(type: "nvarchar(256)", maxLength: 256, nullable: true),
                Email = table.Column<string>(type: "nvarchar(256)", maxLength: 256, nullable: true),
                NormalizedEmail = table.Column<string>(type: "nvarchar(256)", maxLength: 256, nullable: true),
                EmailConfirmed = table.Column<bool>(type: "bit", nullable: false),
                PasswordHash = table.Column<string>(type: "nvarchar(max)", nullable: true),
                SecurityStamp = table.Column<string>(type: "nvarchar(max)", nullable: true),
                ConcurrencyStamp = table.Column<string>(type: "nvarchar(max)", nullable: true),
                PhoneNumber = table.Column<string>(type: "nvarchar(max)", nullable: true),
                PhoneNumberConfirmed = table.Column<bool>(type: "bit", nullable: false),
                TwoFactorEnabled = table.Column<bool>(type: "bit", nullable: false),
                LockoutEnd = table.Column<DateTimeOffset>(type: "datetimeoffset", nullable: true),
                LockoutEnabled = table.Column<bool>(type: "bit", nullable: false),
                AccessFailedCount = table.Column<int>(type: "int", nullable: false)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_AspNetUsers", x => x.Id);
                table.ForeignKey(
                    name: "FK_AspNetUsers_AspNetUsers_ReferrerId",
                    column: x => x.ReferrerId,
                    principalTable: "AspNetUsers",
                    principalColumn: "Id");
            });

        migrationBuilder.CreateTable(
            name: "AspNetRoleClaims",
            columns: table => new
            {
                Id = table.Column<int>(type: "int", nullable: false)
                    .Annotation("SqlServer:Identity", "1, 1"),
                RoleId = table.Column<string>(type: "nvarchar(450)", nullable: false),
                ClaimType = table.Column<string>(type: "nvarchar(max)", nullable: true),
                ClaimValue = table.Column<string>(type: "nvarchar(max)", nullable: true)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_AspNetRoleClaims", x => x.Id);
                table.ForeignKey(
                    name: "FK_AspNetRoleClaims_AspNetRoles_RoleId",
                    column: x => x.RoleId,
                    principalTable: "AspNetRoles",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
            });

        migrationBuilder.CreateTable(
            name: "AspNetUserClaims",
            columns: table => new
            {
                Id = table.Column<int>(type: "int", nullable: false)
                    .Annotation("SqlServer:Identity", "1, 1"),
                UserId = table.Column<string>(type: "nvarchar(450)", nullable: false),
                ClaimType = table.Column<string>(type: "nvarchar(max)", nullable: true),
                ClaimValue = table.Column<string>(type: "nvarchar(max)", nullable: true)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_AspNetUserClaims", x => x.Id);
                table.ForeignKey(
                    name: "FK_AspNetUserClaims_AspNetUsers_UserId",
                    column: x => x.UserId,
                    principalTable: "AspNetUsers",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
            });

        migrationBuilder.CreateTable(
            name: "AspNetUserLogins",
            columns: table => new
            {
                LoginProvider = table.Column<string>(type: "nvarchar(128)", maxLength: 128, nullable: false),
                ProviderKey = table.Column<string>(type: "nvarchar(128)", maxLength: 128, nullable: false),
                ProviderDisplayName = table.Column<string>(type: "nvarchar(max)", nullable: true),
                UserId = table.Column<string>(type: "nvarchar(450)", nullable: false)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_AspNetUserLogins", x => new { x.LoginProvider, x.ProviderKey });
                table.ForeignKey(
                    name: "FK_AspNetUserLogins_AspNetUsers_UserId",
                    column: x => x.UserId,
                    principalTable: "AspNetUsers",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
            });

        migrationBuilder.CreateTable(
            name: "AspNetUserRoles",
            columns: table => new
            {
                UserId = table.Column<string>(type: "nvarchar(450)", nullable: false),
                RoleId = table.Column<string>(type: "nvarchar(450)", nullable: false)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_AspNetUserRoles", x => new { x.UserId, x.RoleId });
                table.ForeignKey(
                    name: "FK_AspNetUserRoles_AspNetRoles_RoleId",
                    column: x => x.RoleId,
                    principalTable: "AspNetRoles",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
                table.ForeignKey(
                    name: "FK_AspNetUserRoles_AspNetUsers_UserId",
                    column: x => x.UserId,
                    principalTable: "AspNetUsers",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
            });

        migrationBuilder.CreateTable(
            name: "AspNetUserTokens",
            columns: table => new
            {
                UserId = table.Column<string>(type: "nvarchar(450)", nullable: false),
                LoginProvider = table.Column<string>(type: "nvarchar(128)", maxLength: 128, nullable: false),
                Name = table.Column<string>(type: "nvarchar(128)", maxLength: 128, nullable: false),
                Value = table.Column<string>(type: "nvarchar(max)", nullable: true)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_AspNetUserTokens", x => new { x.UserId, x.LoginProvider, x.Name });
                table.ForeignKey(
                    name: "FK_AspNetUserTokens_AspNetUsers_UserId",
                    column: x => x.UserId,
                    principalTable: "AspNetUsers",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
            });

        migrationBuilder.CreateIndex(
            name: "IX_AspNetRoleClaims_RoleId",
            table: "AspNetRoleClaims",
            column: "RoleId");

        migrationBuilder.CreateIndex(
            name: "RoleNameIndex",
            table: "AspNetRoles",
            column: "NormalizedName",
            unique: true,
            filter: "[NormalizedName] IS NOT NULL");

        migrationBuilder.CreateIndex(
            name: "IX_AspNetUserClaims_UserId",
            table: "AspNetUserClaims",
            column: "UserId");

        migrationBuilder.CreateIndex(
            name: "IX_AspNetUserLogins_UserId",
            table: "AspNetUserLogins",
            column: "UserId");

        migrationBuilder.CreateIndex(
            name: "IX_AspNetUserRoles_RoleId",
            table: "AspNetUserRoles",
            column: "RoleId");

        migrationBuilder.CreateIndex(
            name: "EmailIndex",
            table: "AspNetUsers",
            column: "NormalizedEmail");

        migrationBuilder.CreateIndex(
            name: "IX_AspNetUsers_ReferrerId",
            table: "AspNetUsers",
            column: "ReferrerId");

        migrationBuilder.CreateIndex(
            name: "UserNameIndex",
            table: "AspNetUsers",
            column: "NormalizedUserName",
            unique: true,
            filter: "[NormalizedUserName] IS NOT NULL");
    }

    protected override void Down(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.DropTable(
            name: "AspNetRoleClaims");

        migrationBuilder.DropTable(
            name: "AspNetUserClaims");

        migrationBuilder.DropTable(
            name: "AspNetUserLogins");

        migrationBuilder.DropTable(
            name: "AspNetUserRoles");

        migrationBuilder.DropTable(
            name: "AspNetUserTokens");

        migrationBuilder.DropTable(
            name: "AspNetRoles");

        migrationBuilder.DropTable(
            name: "AspNetUsers");
    }
}

Answer 1

您可以通过修改如下关系来手动修复迁移文件：

 constraints: table =>
            {
                table.PrimaryKey("PK_AspNetUsers", x => x.Id);
                table.ForeignKey(
                    name: "FK_AspNetUsers_AspNetUsers_ReferrerId",
                    column: x => x.ReferrerId,
                    principalTable: "AspNetUsers",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.NoAction);
            });

或者您可以删除此迁移并添加另一个包含正确onDelete操作的迁移，正如我在评论中提到的那样。