添加新对象会导致重复密钥冲突

Question

我有这门课：

public class User
{
    /// <summary>
    /// Unique identifier and database table key of a User.
    /// </summary>
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int ID { get; set; }

    /// <summary> Name of the User. </summary>
    public string Username { get; set; }

    /// <summary> Password of the User. </summary>
    public string Password { get; set; }

    /// <summary> Role the User is assigned to. </summary>
    public Role Role { get; set; }
}

如果我创建一个新用户并将其添加到 DbSet<User>：

User newUser = new User
{
    Password = passwordHash,
    Username = username,
    Role = dbRole
};


_context.Entry(newUser).State = EntityState.Added;

_context.Users.Add(newUser);

_context.SaveChanges();

我收到此错误：

An exception occurred in the database while saving changes for context type 'webbackend.DBContext'.
    Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.
    ---> Npgsql.PostgresException (0x80004005): 23505: duplicate key value violates unique constraint "PK_Users"

如果通过将属性 ID 设置为 get-only public int ID { get; } 这会导致我的代码的另一个位置出现问题，我可以摆脱这种情况的唯一方法。

如何让实体框架为新用户分配正确递增的 ID？

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<User>().HasKey(u => u.ID);
    modelBuilder.Entity<User>().ToTable("Users");
}