How to create many-to-many relationship with custom ApplicationUser class MVC?

Question

I need to link two tables (AspNetUsers which uses custom ApplicationUser class, and a custom Projects class). I want the users to have multiple projects, and vice versa. I have added the following code into both of my models; however, when doing migrations and updating the database, no linking table is created.

Here is my ApplicationUser class:

using System;
using System.Security.Claims;
using IssueTracker.Models;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Identity;

namespace IssueTracker.Areas.Identity.Data
{
    public class ApplicationUser : IdentityUser
    {
        public ApplicationUser()
        {
            this.Projects = new HashSet<ProjectModel>();
        }

        public String? FirstName { get; set; }

        public String? LastName { get; set; }

        public String? Role { get; set; }

        public virtual ICollection<ProjectModel> Projects { get; set; }
    }
}

and here is my Project model class:

using System;
using Microsoft.AspNetCore.Identity;
using IssueTracker.Areas.Identity.Data;
using System.ComponentModel.DataAnnotations;

namespace IssueTracker.Models
{
    public class ProjectModel
    {
        public ProjectModel()
        {
            this.Users = new HashSet<ApplicationUser>();
        }

        public int Id { get; set; }

        public string? Name { get; set; }

        public string? Description { get; set; }

        public virtual ICollection<ApplicationUser> Users { get; set; }

    }
}

and here is my DbContext:

using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using IssueTracker.Models;

namespace IssueTracker.Areas.Identity.Data;

public class IssueTrackerIdentityDbContext : IdentityDbContext<ApplicationUser>
{
    public DbSet<ProjectModel> Projects { get; set; }

    public IssueTrackerIdentityDbContext()
    {

    }

    public IssueTrackerIdentityDbContext(DbContextOptions<IssueTrackerIdentityDbContext> options)
        : base(options)
    {
    }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);
        // Customize the ASP.NET Identity model and override the defaults if needed.
        // For example, you can rename the ASP.NET Identity table names and more.
        // Add your customizations after calling base.OnModelCreating(builder);

        builder.ApplyConfiguration(new ApplicationUserEntityConfiguration());
    }


}

public class ApplicationUserEntityConfiguration : IEntityTypeConfiguration<ApplicationUser>
{
    public void Configure(EntityTypeBuilder<ApplicationUser> builder)
    {
        builder.Property(u => u.FirstName).HasMaxLength(255);
        builder.Property(u => u.LastName).HasMaxLength(255);
    }
}

After running a migration with the code above, I am given this migration which does not create a table to link the two.

using Microsoft.EntityFrameworkCore.Migrations;

#nullable disable

namespace IssueTracker.Migrations
{
    public partial class UserProjectTable : Migration
    {
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.RenameColumn(
                name: "ID",
                table: "Projects",
                newName: "Id");

            migrationBuilder.AddColumn<string>(
                name: "ApplicationUserId",
                table: "Projects",
                type: "TEXT",
                nullable: true);

            migrationBuilder.CreateIndex(
                name: "IX_Projects_ApplicationUserId",
                table: "Projects",
                column: "ApplicationUserId");

            migrationBuilder.AddForeignKey(
                name: "FK_Projects_AspNetUsers_ApplicationUserId",
                table: "Projects",
                column: "ApplicationUserId",
                principalTable: "AspNetUsers",
                principalColumn: "Id");
        }

        protected override void Down(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.DropForeignKey(
                name: "FK_Projects_AspNetUsers_ApplicationUserId",
                table: "Projects");

            migrationBuilder.DropIndex(
                name: "IX_Projects_ApplicationUserId",
                table: "Projects");

            migrationBuilder.DropColumn(
                name: "ApplicationUserId",
                table: "Projects");

            migrationBuilder.RenameColumn(
                name: "Id",
                table: "Projects",
                newName: "ID");
        }
    }
}

How should I update my code so that I can properly create a many-to-many relationship between ApplicationUser and Projects. Also, once this relationship is created, how can I properly access and modify the relationship. Do I need to update all 3 classes whenever a user is added to a project (or vice versa), or do I solely need to update the linking table. Thank you so much. I am new to MVC so forgive me if this is very rudimentary.

Answer 1

try this too:

public class ApplicationUserEntityConfiguration : 
IEntityTypeConfiguration<ApplicationUser>
{
public void Configure(EntityTypeBuilder<ApplicationUser> builder)
{
    builder.Property(u => u.FirstName).HasMaxLength(255);
    builder.Property(u => u.LastName).HasMaxLength(255);


    builder.HasMany(x => x.Projects).WithMany(x => x.Users);
}
}