如何在 asp.net-core 中使用代码优先迁移删除唯一约束

Question

I have a project for which I added an initial migration with a foreign key as follows:

 public class ApplicationUser : IdentityUser 
 {
  public string RegistrarId { get; set; }
 
  [ForeignKey("RegistrarId")]
  public virtual ApplicationUser Registrar { get; set; }

 }

However, I realized that when I run the code-first migration, it is automatically creating a unique index on the Registrar column which is against my wish.

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

My question is, Is there a way to modify my class to remove this constraint with another migration.

Below is what I have for the ApplicationUser entity onModelCreating

 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<ApplicationUser>(b =>
        {
            // Each User can have many UserClaims
            b.HasMany(e => e.Claims)
                .WithOne(e => e.User)
                .HasForeignKey(uc => uc.UserId)
                .IsRequired();

            // Each User can have many UserLogins
            b.HasMany(e => e.Logins)
                .WithOne(e => e.User)
                .HasForeignKey(ul => ul.UserId)
                .IsRequired();

            // Each User can have many UserTokens
            b.HasMany(e => e.Tokens)
                .WithOne(e => e.User)
                .HasForeignKey(ut => ut.UserId)
                .IsRequired();

            // Each User can have many entries in the UserRole join table
            b.HasMany(e => e.UserRoles)
                .WithOne(e => e.User)
                .HasForeignKey(ur => ur.UserId)
                .IsRequired();

            b.HasIndex(e => e.Email)
                .IsUnique();             
        });

My application is on ASP.NET-Core 3.1 with EF-Core 3.1 and SQLServer

Please help Thank you

Answer 1

It is very likely that you have unique index configured in OnModelCreating . If you do, just flip it to false.

protected override void OnModelCreating(ModelBuilder builder)
{
    builder.Entity<ApplicationUser>()
        .HasIndex(x => x.RegistrarId)
        .IsUnique(false);

    base.OnModelCreating(builder);
}

It will generate "drop and create" index migration, but without unique attribute

protected override void Up(MigrationBuilder migrationBuilder)
{
    migrationBuilder.DropIndex(
        name: "IX_AspNetUsers_RegistrarId",
        table: "AspNetUsers");

    migrationBuilder.CreateIndex(
        name: "IX_AspNetUsers_RegistrarId",
        table: "AspNetUsers",
        column: "RegistrarId");
}