code frist方式:
User表
Role表
UsersInRoles表
User：
public class User
  {
  public string UserId { get; set; }
  public string UserName { get; set; }
  public virtual ICollection<User> Roles { get; set; }
｝




Role:
 public class Role
  {
  public string RoleId { get; set; }
  public string RoleName { get; set; }
  public virtual ICollection<Role> Roles { get; set; }

}


 
public class DbEntities : DbContext
  {
public IDbSet<User> Users { get; set; }
public IDbSet<Role> Roles { get; set; }

 modelBuilder.Entity<User>().Property(i => i.UserId)
.HasDatabaseGen eratedOption(DatabaseGeneratedOption.None);
 modelBuilder.Entity<User>()
  .HasMany(u=>u.Roles)
  .WithMany(u=>u.Users)
  .Map(m =>
  {
  m.ToTable("UsersInRoles");
  m.MapLeftKey("UserId");
  m.MapRightKey("RoleId");
  });
}

现在我想删除UsersInRoles中数据，如何删除