自動生成的備用密鑰

Question

EF Core正在為以下數據模型生成備用密鑰（ AK_UserRoles_UserId_RoleId ）：

資料模型

 public class User : IdentityUser<Guid>
{
    [MaxLength(50)]
    public String FirstName { get; set; }

    [MaxLength(50)]
    public String LastName { get; set; }

    public virtual ICollection<UserRole> UserRoles { get; set; }
}

public class Role : IdentityRole<Guid>
{
    public string Description { get; set; }

    public virtual ICollection<UserGroupToRole> UserGroups { get; set; }
}


public class UserRole : IdentityUserRole<Guid>
{
    public Guid Id { get; set; }

    public virtual User User { get; set; }

    public virtual Role Role { get; set; }

    public int? EntityId { get; set; }

    public string EntityType { get; set; }
}

模型制作者

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

        builder.Entity<User>(i =>
        {
            i.ToTable("Users");
            i.HasKey(x => x.Id);
            i.Property(u => u.Id).HasDefaultValueSql("NEWID()");

            i.HasMany(u => u.UserRoles)
                .WithOne(ur => ur.User)
                .HasForeignKey(ur => ur.UserId)
                .IsRequired();
        });

        builder.Entity<Role>(i =>
        {
            i.ToTable("Roles");
            i.HasKey(x => x.Id);
            i.Property(u => u.Id).HasDefaultValueSql("NEWID()");
            i.HasMany(x => x.UserGroups);

            i.HasMany<UserRole>()
                .WithOne(ur => ur.Role)
                .HasForeignKey(ur => ur.RoleId)
                .IsRequired();
        });

        builder.Entity<UserRole>(i =>
        {
            i.ToTable("UserRoles");
            i.HasKey(x => x.Id);
            i.Property(x => x.Id).HasDefaultValueSql("NEWID()");
            i.HasIndex(x => new { x.UserId, x.RoleId, x.EntityId, x.EntityType }).IsUnique();
        });

    }

結果遷移

 migrationBuilder.CreateTable(
            name: "UserRoles",
            columns: table => new
            {
                Id = table.Column<Guid>(nullable: false, defaultValueSql: "NEWID()"),
                EntityId = table.Column<int>(nullable: true),
                EntityType = table.Column<string>(nullable: false),
                RoleId = table.Column<Guid>(nullable: false),
                UserId = table.Column<Guid>(nullable: false)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_UserRoles", x => x.Id);
                table.UniqueConstraint("AK_UserRoles_UserId_RoleId", x => new { x.UserId, x.RoleId });
                table.ForeignKey(
                    name: "FK_UserRoles_Roles_RoleId",
                    column: x => x.RoleId,
                    principalTable: "Roles",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
                table.ForeignKey(
                    name: "FK_UserRoles_Users_UserId",
                    column: x => x.UserId,
                    principalTable: "Users",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
            });

上面的AK_UserRoles_UserId_RoleId是有問題的。 我不希望這成為約束。 如何調整模型以允許約定不應用唯一約束，或者如何在模型構建器中進行調整呢？

Answer 1

EF Core不會自動生成備用密鑰。 在此特定情況下，由於基礎IdentityDbContext實現（在base.OnModelCreating(builder);調用內部）將{ UserId, RoleId }定義為UserRole表的主鍵，因此生成了該表。 當您的代碼將Id設置為主鍵時，EF Core不會替換舊的Id ，而是將其轉換為備用鍵。

沒有有效的API來刪除密鑰，因此您必須直接使用可變元數據模型。 最簡單的方法是在定義新主鍵之前刪除舊主鍵：

builder.Entity<UserRole>(i =>
{
    i.Metadata.RemoveKey(i.Metadata.FindPrimaryKey().Properties);
    // ...
});