entity-framework - 如何在 DB first 方法中为实体设置创建日期和修改日期

Question

在我们应用程序的每个 SQL 表中，我们都有“CreatedDate”和“ModifiedDate”列。我们正在使用数据库优先方法。当我保存数据时，我希望这两列自动填充。一种方法是将默认值设置为 getdate()在 SQL 表列本身上。所以这将部分解决问题。这意味着它将在实体为新实体时设置 CreatedDate 和 ModifiedDate。
但是，当我编辑/更新实体时，我只想要 ModifiedDate要被更新。
有很多文章使用代码优先的方法来做这件事。但我们使用的是数据库优先方法。
我在这里有什么选择？

Answer 1

查看 .NET Core 的答案:
https://stackoverflow.com/a/64824067/3850405
我喜欢这样使用的更通用的方法:

interface IEntityDate
{
    DateTime CreatedDate { get; set; }

    DateTime UpdatedDate { get; set; }
}

public abstract class EntityBase<T1>: IEntityDate
{
    public T1 Id { get; set; }

    public virtual DateTime CreatedDate { get; set; }
    public virtual string CreatedBy { get; set; }
    public virtual DateTime UpdatedDate { get; set; }
    public virtual string UpdatedBy { get; set; }
}

public override int SaveChanges()
{
    var now = DateTime.UtcNow;

    foreach (var changedEntity in ChangeTracker.Entries())
    {
        if (changedEntity.Entity is IEntityDate entity)
        {
            switch (changedEntity.State)
            {
                case EntityState.Added:
                    entity.CreatedDate = now;
                    entity.UpdatedDate = now;
                    break;

                case EntityState.Modified:
                    Entry(entity).Property(x => x.CreatedDate).IsModified = false;
                    entity.UpdatedDate = now;
                    break;
            }
        }
    }

    return base.SaveChanges();
}

更新:
办理 CreatedBy和 UpdatedBy我使用 DbContext 的包装器，如下所示:

public interface IEntity
{
    DateTime CreatedDate { get; set; }

    string CreatedBy { get; set; }

    DateTime UpdatedDate { get; set; }

    string UpdatedBy { get; set; }
}

public interface ICurrentUser
{
    string GetUsername();
}

public class ApplicationDbContextUserWrapper
{
    public ApplicationDbContext Context;

    public ApplicationDbContextUserWrapper(ApplicationDbContext context, ICurrentUser currentUser)
    {
        context.CurrentUser = currentUser;
        this.Context = context;
    }
}

public class ApplicationDbContext : DbContext
{

    public ICurrentUser CurrentUser;
    
    public override int SaveChanges()
    {
        var now = DateTime.UtcNow;

        foreach (var changedEntity in ChangeTracker.Entries())
        {
            if (changedEntity.Entity is IEntity entity)
            {
                switch (changedEntity.State)
                {
                    case EntityState.Added:
                        entity.CreatedDate = now;
                        entity.UpdatedDate = now;
                        entity.CreatedBy = CurrentUser.GetUsername();
                        entity.UpdatedBy = CurrentUser.GetUsername();
                        break;
                    case EntityState.Modified:
                        Entry(entity).Property(x => x.CreatedBy).IsModified = false;
                        Entry(entity).Property(x => x.CreatedDate).IsModified = false;
                        entity.UpdatedDate = now;
                        entity.UpdatedBy = CurrentUser.GetUsername();
                        break;
                }
            }
        }

        return base.SaveChanges();
    }
    
    ...