当我迁移多对多关系时，为什么实体框架会生成“EmployeesProjects”？我已经定义了另一个？

Question

我有两个实体：

Employeees

和项目，它们具有多对多的关系。我为此定义了一个

ProjectEmployee

，但是当我添加迁移时，它仍然会创建一个

EmployeesProjects

。为什么会发生这种情况以及如何解决？谢谢你们！

这里是

Employees.cs

using Day1.Model;
using System.ComponentModel.DataAnnotations;

public class Employees
{
    [Required]
    public int Id { get; set; }
    [Required]
    [MaxLength(50)]
    public string Name { get; set; }
    public int DepartmentId { get; set; }
    public DateTime JoinedDate { get; set; }
    public Salaries Salary { get; set; }
    public IList<Projects> Projects { get; set; }
    public Departments Department { get; set; }
    public IList<ProjectEmployee> ProjectEmployees { get; set; }
}

Projects.cs

using Day1.Model;
using System.ComponentModel.DataAnnotations;

public class Projects
{
    [Required]
    public int Id { get; set; }
    [Required]
    [MaxLength(50)]
    public string Name { get; set; }
    public IList<Employees> Employees { get; set; }
    public IList<ProjectEmployee> ProjectEmployees { get; set; }
}

ProjectEmployee.cs

namespace Day1.Model
{
    public class ProjectEmployee
    {
        public int ProjectId { get; set; }
        public Projects Project { get; set; }
        public int EmployeeId { get; set; }
        public Employees Employee { get; set; }
        public bool Enable { get; set; }
    }
}

这是迁移：

using System;
using Microsoft.EntityFrameworkCore.Migrations;

#nullable disable

#pragma warning disable CA1814 // Prefer jagged arrays over multidimensional

namespace Day1.Migrations
{
    /// <inheritdoc />
    public partial class InitialCreate : Migration
    {
        /// <inheritdoc />
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.CreateTable(
                name: "Departments",
                columns: table => new
                {
                    Id = table.Column<int>(type: "int", nullable: false)
                        .Annotation("SqlServer:Identity", "1, 1"),
                    Name = table.Column<string>(type: "nvarchar(50)", maxLength: 50, nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Departments", x => x.Id);
                });

            migrationBuilder.CreateTable(
                name: "Projects",
                columns: table => new
                {
                    Id = table.Column<int>(type: "int", nullable: false)
                        .Annotation("SqlServer:Identity", "1, 1"),
                    Name = table.Column<string>(type: "nvarchar(50)", maxLength: 50, nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Projects", x => x.Id);
                });

            migrationBuilder.CreateTable(
                name: "Employees",
                columns: table => new
                {
                    Id = table.Column<int>(type: "int", nullable: false)
                        .Annotation("SqlServer:Identity", "1, 1"),
                    Name = table.Column<string>(type: "nvarchar(50)", maxLength: 50, nullable: false),
                    DepartmentId = table.Column<int>(type: "int", nullable: false),
                    JoinedDate = table.Column<DateTime>(type: "datetime2", nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Employees", x => x.Id);
                    table.ForeignKey(
                        name: "FK_Employees_Departments_DepartmentId",
                        column: x => x.DepartmentId,
                        principalTable: "Departments",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                });

            migrationBuilder.CreateTable(
                name: "EmployeesProjects",
                columns: table => new
                {
                    EmployeesId = table.Column<int>(type: "int", nullable: false),
                    ProjectsId = table.Column<int>(type: "int", nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_EmployeesProjects", x => new { x.EmployeesId, x.ProjectsId });
                    table.ForeignKey(
                        name: "FK_EmployeesProjects_Employees_EmployeesId",
                        column: x => x.EmployeesId,
                        principalTable: "Employees",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                    table.ForeignKey(
                        name: "FK_EmployeesProjects_Projects_ProjectsId",
                        column: x => x.ProjectsId,
                        principalTable: "Projects",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                });

            migrationBuilder.CreateTable(
                name: "ProjectEmployees",
                columns: table => new
                {
                    ProjectId = table.Column<int>(type: "int", nullable: false),
                    EmployeeId = table.Column<int>(type: "int", nullable: false),
                    Enable = table.Column<bool>(type: "bit", nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_ProjectEmployees", x => new { x.ProjectId, x.EmployeeId });
                    table.ForeignKey(
                        name: "FK_ProjectEmployees_Employees_EmployeeId",
                        column: x => x.EmployeeId,
                        principalTable: "Employees",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                    table.ForeignKey(
                        name: "FK_ProjectEmployees_Projects_ProjectId",
                        column: x => x.ProjectId,
                        principalTable: "Projects",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                });

            migrationBuilder.CreateTable(
                name: "Salaries",
                columns: table => new
                {
                    Id = table.Column<int>(type: "int", nullable: false)
                        .Annotation("SqlServer:Identity", "1, 1"),
                    EmployeeId = table.Column<int>(type: "int", nullable: false),
                    Salary = table.Column<int>(type: "int", nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Salaries", x => x.Id);
                    table.ForeignKey(
                        name: "FK_Salaries_Employees_EmployeeId",
                        column: x => x.EmployeeId,
                        principalTable: "Employees",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                });

            migrationBuilder.InsertData(
                table: "Departments",
                columns: new[] { "Id", "Name" },
                values: new object[,]
                {
                    { 1, "Software Development" },
                    { 2, "Finance" },
                    { 3, "Accountant" },
                    { 4, "HR" }
                });

            migrationBuilder.CreateIndex(
                name: "IX_Employees_DepartmentId",
                table: "Employees",
                column: "DepartmentId");

            migrationBuilder.CreateIndex(
                name: "IX_EmployeesProjects_ProjectsId",
                table: "EmployeesProjects",
                column: "ProjectsId");

            migrationBuilder.CreateIndex(
                name: "IX_ProjectEmployees_EmployeeId",
                table: "ProjectEmployees",
                column: "EmployeeId");

            migrationBuilder.CreateIndex(
                name: "IX_Salaries_EmployeeId",
                table: "Salaries",
                column: "EmployeeId",
                unique: true);
        }

        /// <inheritdoc />
        protected override void Down(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.DropTable(
                name: "EmployeesProjects");

            migrationBuilder.DropTable(
                name: "ProjectEmployees");

            migrationBuilder.DropTable(
                name: "Salaries");

            migrationBuilder.DropTable(
                name: "Projects");

            migrationBuilder.DropTable(
                name: "Employees");

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

我尝试在迁移中手动删除EmployeesProjects表创建代码块，但当我添加迁移时它仍然会生成它。我搜索了每个文件，看看我是否在任何地方配置了模型，但结果并不那么积极。

Answer 1

由于我已经定义了 ProjectEmployee 实体，所以包含没有用

    public IList<Employee> Employees { get; set; }

在Employees.cs 和

    public IList<Employee> Employees { get; set; }

在 Projects.cs 中。 系统会自动生成一个实体来插入多对多关系，即使已经存在一个实体。