小编use*_*311的帖子

我有以下实体模型:

public class Todo  
{  
    [Required]  
    public int ID { get; set; }  
    public int OrderId { get; set; } //Not required  
    public string Description { get; set; }  
    public bool Finished { get; set; }  
    public DateTime CreationDate { get; set; }  
    public int Priority { get; set; } //Not required  
    public string CreatedBy { get; set; }  
    public bool Deleted { get; set; }  
}

在相应的数据库表中,所有字段都创建为"not null".我想允许一些字段为空.我该怎么做呢？