实体框架7审核日志

我正在将一个旧项目移植到ASP.NET 5和Entity Framework 7.我已经使用数据库第一种方法(DNX scaffold)来创建模型.

旧项目基于实体框架4,审计跟踪是通过覆盖以下SaveChanges方法实现的DbContext:

public override int SaveChanges(System.Data.Objects.SaveOptions options)
{
    int? UserId = null;
    if (System.Web.HttpContext.Current != null) 
        UserId = (from user in Users.Where(u => u.UserName == System.Web.HttpContext.Current.User.Identity.Name) select user.Id).SingleOrDefault();

    foreach (ObjectStateEntry entry in ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified))
    {
        Type EntityType = entry.Entity.GetType();

        PropertyInfo pCreated = EntityType.GetProperty("Created");
        PropertyInfo pCreatedById = EntityType.GetProperty("CreatedById");
        PropertyInfo pModified = EntityType.GetProperty("Modified");
        PropertyInfo pModifiedById = EntityType.GetProperty("ModifiedById");

        if (entry.State == EntityState.Added)
        {
            if (pCreated != null)
                pCreated.SetValue(entry.Entity, DateTime.Now, new object[0]);
            if (pCreatedById != null && UserId != null)
                pCreatedById.SetValue(entry.Entity, UserId, new object[0]);
        }
        if (pModified != null)
            pModified.SetValue(entry.Entity, DateTime.Now, new object[0]);
        if (pModifiedById != null && UserId != null)
            pModifiedById.SetValue(entry.Entity, UserId, new object[0]);
        }
    }

    return base.SaveChanges(options);
}

我的问题是,我如何在Entity Framework 7中实现这一点？我必须先采用代码方法吗？

基本上你有两种方法来实现这个目标:

使用ChangeTracker API(EF 6+):

这是我们目前在EF 6中的方式,它仍然有效并适用于EF 7:

首先,您必须确保您的实体正在为审计字段实现通用接口:

public interface IAuditableEntity 
{
    int? CreatedById { get; set; }

    DateTime Created { get; set; }

    int? ModifiedById { get; set; }

    DateTime Modified { get; set; }
}

然后,您可以覆盖SaveChanges并使用审计值更新每个公共字段:

public override int SaveChanges()
{
    int? userId = null;
    if (System.Web.HttpContext.Current != null)
        userId = (from user in Users.Where(u => u.UserName == System.Web.HttpContext.Current.User.Identity.Name) select user.Id).SingleOrDefault();

    var modifiedEntries = ChangeTracker.Entries()
            .Where(e => e.State == EntityState.Added || e.State == EntityState.Modified);

    foreach (EntityEntry entry in modifiedEntries)
    {
        entry.Entity.ModifiedById = UserId;
        entry.Entity.Modified = DateTime.Now;

        if (entry.State == EntityState.Added)
        {
            entry.Entity.CreatedById = UserId;
            entry.Entity.Created = DateTime.Now;
        }
    }

    return base.SaveChanges();
}

使用EF 7新的"阴影属性"功能:

阴影属性是实体类中不存在的属性.这些属性的值和状态仅在Change Tracker中维护.

换句话说,审核列不会在您的实体上公开,与上面的实体相比,它们似乎是一个更好的选择.

要实现阴影属性,首先必须在实体上配置它们.比方说,你有一个需要有一些审计列的User对象:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity().Property("CreatedById");

    modelBuilder.Entity().Property("Created");

    modelBuilder.Entity().Property("ModifiedById");

    modelBuilder.Entity().Property("Modified");
}

配置完成后,您现在可以在SaveChanges()覆盖上访问它们并相应地更新它们的值:

public override int SaveChanges()
{
    int? userId = null;
    if (System.Web.HttpContext.Current != null)
        userId = (from user in Users.Where(u => u.UserName == System.Web.HttpContext.Current.User.Identity.Name) select user.Id).SingleOrDefault();

    var modifiedBidEntries = ChangeTracker.Entries()
        .Where(e => e.State == EntityState.Added || e.State == EntityState.Modified);

    foreach (EntityEntry entry in modifiedBidEntries)
    {
        entry.Property("Modified").CurrentValue = DateTime.UtcNow;
        entry.Property("ModifiedById").CurrentValue = userId;

        if (entry.State == EntityState.Added)
        {
            entry.Property("Created").CurrentValue = DateTime.UtcNow;
            entry.Property("CreatedById").CurrentValue = userId;
        }
    }

    return base.SaveChanges();
}

最后的想法:

为了实现像审计列这样的东西,我将采用阴影属性方法,因为这些是交叉关注的问题,并不一定属于我的域对象,因此以这种方式实现它们将使我的域对象保持良好和干净.