asp.net-mvc – EF 4.1 Code First：“非空值类型’DateTime’”

但是我收到与“datetime”类型的Date1类型相关的错误.

The 'Date1' property on 'StaffAttachment' could not be set to a 'null' value. You must set this property to a non-null value of type 'DateTime'.

这是告诉我,日期中的所有行都必须有日期,而不是空吗？如果我不想在特定行上设置日期,该怎么办？

任何人都可以提供解决这个问题的建议？

谢谢保罗

编辑1(过帐模型)

public class StaffAttachment
{
    [Key]
    public int AttachmentID { get; set; }

    public int? StaffID { get; set; }

    public int? TypeID { get; set; }

    [Required]
    [DisplayName("Proof of ID")]
    public int? AttachmentTypeID { get; set; }

    [Required]
    [DisplayName("ID Reference")]
    public string Reference1 { get; set; }

    public string Reference2 { get; set; }

    public string DateType { get; set; }

    [DisplayName("Expiry Date")]
    public DateTime Date1 { get; set; }

    [Required]
    public DateTime Date2 { get; set; }

    public DateTime Date3 { get; set; }

    public DateTime Date4 { get; set; }

    public string AttachmentPath { get; set; }

    public int? ValidatedUserID { get; set; }

    public DateTime ValidatedDate { get; set; }

    public int? CreatedUserID { get; set; }

    public DateTime CreatedDate { get; set; }

    public int? EditedUserID { get; set; }

    public DateTime EditedDate { get; set; }

    public TimeSpan TimeStamp { get; set; }

    public string FileName { get; set; }

    public byte[] FileImage { get; set; }

    public int AttachmentSection { get; set; }
}