如何在实体框架中清除跟踪的实体

问题描述

我正在运行一些修正代码，运行在一大堆实体上，因为它的速度降低，这是因为跟踪的实体数量在每个迭代中增加，可能需要很长时间才能保存更改在每次迭代结束时。每次迭代都是独立的，不会改变先前加载的实体。

我知道我可以关闭更改跟踪，但我不想，因为它不是大量插入代码，而是加载实体并计算一些事情，如果数字不正确设置新数字并更新/删除/创建一些其他实体。我知道我可以为每次迭代创建一个新的DbContext，可能运行速度比在同一个实例中执行的要快，但我认为可能会有更好的方法。

所以问题是有没有办法清除先前在数据库上下文中加载的实体？

解决方案

您可以添加一个方法您的 DbContext 或使用ChangeTracker分离所有添加，修改和删除的实体的扩展方法：

  public void DetachAllEntities（）
 {
 var changedEntriesCopy = this.ChangeTracker.Entries（）
 .Where（e => e.State == EntityState 。添加|| 
 e.State == EntityState.Modified || 
 e.State == EntityState.Deleted）
 .ToList（）; 
 foreach（changeEntriesCopy中的var entity）
 {
 this.Entry（entity.Entity）.State = EntityState.Detached; 
} 
} 
  

I am running some correction code that runs over a big pile of entities, as it progress its speed decreases, that is because the number of tracked entities in the context increase with each iteration, It can take long so I am saving changes at the end of each iteration. Each iteration is independent and does not change the previosuly loaded entities.

I know I can turn off change tracking but I do not want to, because it is not a bulk insert code, but loading the entities and calculating a few things and if the numbers are not correct set the new numbers and update/delete/create some additional entities. I know I can create a new DbContext for each iteration and probably that would run faster than doing all in the same instance, but I am thinking that there might be a better way.

So the question is; Is there a way of clearing the entities previously loaded in the db context?

解决方案

You can add a method to your DbContext or an extension method that uses the ChangeTracker to detach all the Added, Modified, and Deleted entities:

public void DetachAllEntities()
{
    var changedEntriesCopy = this.ChangeTracker.Entries()
        .Where(e => e.State == EntityState.Added ||
                    e.State == EntityState.Modified ||
                    e.State == EntityState.Deleted)
        .ToList();
    foreach (var entity in changedEntriesCopy)
    {
        this.Entry(entity.Entity).State = EntityState.Detached;
    }
}

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