c# - 在 EF 6 中自动生成时间戳(代码优先): conversion of a datetime2 data type to a datetime data is an out-of-range value

Question

我继承了一个类:

 public abstract class BaseEntity 
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid Id { get; set; }


    [DatabaseGenerated(DatabaseGeneratedOption.Computed)]
    public DateTime CreatedAt { get; set; }
}

但是当我尝试持久化实例时(我没有设置 CreatedAt)它失败并出现错误:

{"The conversion of a datetime2 data type to a datetime data type resulted in an out-of-range value.\r\nThe statement has been terminated."}

我做错了什么？

Answer 1

首先创建一个基础实体:

public class Student: BaseEntity
{
    public int StudentID { get; set; }
    public string StudentName { get; set; }
    public DateTime? DateOfBirth { get; set; }
    public decimal Height { get; set; }
    public float Weight { get; set; }
}

public class BaseEntity{ 
    public DateTime CreatedDate { get; set; }
    public DateTime UpdatedDate { get; set; }    
}

然后在您的数据库上下文中覆盖 SaveChanges() 方法。

public override int SaveChanges()
{
    var entries = ChangeTracker
        .Entries()
        .Where(e => e.Entity is BaseEntity && (
                e.State == EntityState.Added
                || e.State == EntityState.Modified));

    foreach (var entityEntry in entries)
    {
        ((BaseEntity)entityEntry.Entity).UpdatedDate = DateTime.Now;

        if (entityEntry.State == EntityState.Added)
        {
            ((BaseEntity)entityEntry.Entity).CreatedDate = DateTime.Now;
        }
    }

    return base.SaveChanges();
}

就是这样。我从 here 中获取了这个示例.在那里查看更多详细信息。