.NET Core 使用 EF 出错的解决方法

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public class ApplicationDbContext : IdentityDbContext<User>

{

    public ApplicationDbContext(DbContextOptions options)
    : base(options)
    {
    }

    public virtual DbSet<User> Users { get; set; }
    public virtual DbSet<Role> Roles { get; set; }
    public virtual DbSet<Group> Groups { get; set; }
    public virtual DbSet<GroupRole> GroupRoles { get; set; }
    public virtual DbSet<Log> Logs { get; set; }
    public virtual DbSet<LogDetail> LogDetails { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    => optionsBuilder.UseSqlServer(
        @"Data Source=.;Initial Catalog=DotNetCore;Persist Security Info=True;User ID=sa;Password=25423456;");

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {

        modelBuilder.Entity<User>()
                     .HasOne(d => d.Group)
                     .WithMany(t => t.Users)
                     .HasForeignKey(d => d.GroupId)
                     .OnDelete(DeleteBehavior.Cascade);

    }

} 

有了模型后，即可通过迁移创建数据库。
运行 dotnet ef migrations add InitialCreate 以为迁移搭建基架，并为模型创建一组初始表。
运行 dotnet ef database update 以将新迁移应用到数据库。 在应用迁移之前，此命令可创建数据库。