实体框架7审核日志 [英] Entity Framework 7 audit log

问题描述

我正在将一个旧项目移植到ASP.NET 5和Entity Framework7.我已经使用数据库优先方法(DNX支架)来创建模型.

I am porting an old project over to ASP.NET 5 and Entity Framework 7. I have used the database first approach (DNX scaffold) to create the model.

旧项目基于Entity Framework 4，并且通过覆盖DbContext的SaveChanges方法来实现审核跟踪:

The old project is based on Entity Framework 4 and audit tracking is implemented by overriding the SaveChanges method of the 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，如何在Entity Framework 7中实现此功能?我必须采用代码优先方法吗?

My question is, how can I implement this in Entity Framework 7? Do I have to take the code first approach?

推荐答案

基本上，您可以通过两种方法来实现:

Basically you have two ways to achieve this:

使用ChangeTracker API(EF 6 +):

这是我们目前在EF 6中执行的方式，它仍然有效并且适用于EF 7:

This is the way we currently do it in EF 6 and it is still valid and working for EF 7:

首先，您必须确保您的实体正在为审核字段实现通用接口:

First you have to make sure your entities are implementing a common interface for audit fields:

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并使用审核值更新每个公共字段:

Then you can override SaveChanges and update each common field with audit values:

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<IAuditableEntity>()
            .Where(e => e.State == EntityState.Added || e.State == EntityState.Modified);

    foreach (EntityEntry<IAuditableEntity> 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新增的阴影属性"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变更跟踪器中维护.

Shadow properties are properties that do not exist in your entity class. The value and state of these properties is maintained purely in the Change Tracker.

换句话说，审计列将不会在您的实体上公开，这与上面必须将其包括在实体中的选择相比，似乎是一个更好的选择.

In other words, the audit columns will not be exposed on your entities which seems to be a better option compare to the one above where you have to include them on your entities.

要实现阴影属性，首先必须在实体上配置它们.例如，假设您有一个User对象，该对象需要一些审核列:

To implement shadow properties, first you have to configure them on your entities. Let's say for example you have a User object that needs to have some audit columns:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<User>().Property<int>("CreatedById");

    modelBuilder.Entity<User>().Property<DateTime>("Created");

    modelBuilder.Entity<User>().Property<int>("ModifiedById");

    modelBuilder.Entity<User>().Property<DateTime>("Modified");
}

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

Once configured, now you can access them on SaveChanges() override and update their values accordingly:

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<User>()
        .Where(e => e.State == EntityState.Added || e.State == EntityState.Modified);

    foreach (EntityEntry<User> 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();
}

最终想法:

对于实现诸如审计列之类的事情，我将采用阴影属性"方法，因为这些是跨领域的关注点，不一定属于我的领域对象，因此以这种方式实现它们将使我的领域对象保持整洁.

For implementing something like audit columns, I'll take the Shadow Properties approach since these are cross cutting concerns and do not necessarily belong to my domain objects so having them implemented this way will keep my domain objects nice and clean.

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