AsNoTracking有关上下文属性，查询还是ChangeTracker？ [英] AsNoTracking on context properties, query or ChangeTracker?

问题描述

我注意到可以通过三种不同的方式禁用跟踪：

• 通过 AsNoTracking 上下文属性

通过执行最终查询之前的 AsNoTracking 进行执行

• 通过 context.ChangeTracker.QueryTrackingBehavior

这三个之间是否有区别

如果我以前在每个上下文属性后都使用了 AsNoTracking ，现在我可以使用这种方法？

是否将其替换为最终查询中的单个调用（或通过 ChangeTracker 禁用它）？

解决方案

AsNoTracking 和 AsTracking 是 IQueryable< T> ，因此与查询的状态相关联，而不是与特定实体相关联（它们在 DbSet< T> 级别可用）只是因为它实现了 IQueryable< T> ）-请注意方法说明中的 all 字样：

AsNoTracking

返回一个新查询，其中更改跟踪程序将不跟踪任何返回的实体。

AsTracking

返回新查询，更改跟踪器将在该查询中跟踪返回的所有实体的更改。

两者都说：

查询的默认跟踪行为可以通过 QueryTrackingBehavior 。

换句话说，如果查询返回实体并且没有 AsNoTracking 或 AsTracking 在查询表达式树中的任意位置调用 ，查询使用 ChangeTracker.QueryTrackingBehavior 的值。

所以您的问题的答案是肯定的，您可以通过对最终查询的单个调用或通过 ChangeTracker 来达到相同的效果。

但是要注意一件事，文档中没有解释。如果查询表达式树包含多个 AsNoTracking / AsTracking 调用，则 last 调用优先。这意味着，通过将 AsNoTracking 添加到最终查询中，或者如果将 AsTracking 添加到最终查询中，则无论其内部如何跟踪行为调用或 ChangeTracker 属性。

I noticed that it is possible to disable tracking in three different ways:

• via AsNoTracking on context properties
• via AsNoTracking on the final query before executing it
• via context.ChangeTracker.QueryTrackingBehavior

Is there any difference between these three approaches if I want to disable tracking for everything?

If I previously used AsNoTracking after each context property and now I replace it with only a single call on the final query (or disable it via the ChangeTracker) will it have the same effect?

解决方案

AsNoTracking and AsTracking are extension methods of IQueryable<T>, thus are associated with the state of the query and not a specific entity (the fact that they are available at DbSet<T> level is just because it implements IQueryable<T>) - note the word all inside the method descriptions:

AsNoTracking

Returns a new query where the change tracker will not track any of the entities that are returned.

AsTracking

Returns a new query where the change tracker will keep track of changes for all entities that are returned.

And both say:

The default tracking behavior for queries can be controlled by QueryTrackingBehavior.

In other words, if the query returns entities and there is no AsNoTracking or AsTracking calls anywhere in the query expression tree, the query uses the value of the ChangeTracker.QueryTrackingBehavior.

So the answer to your question is yes, you can achieve the same effect with a single call on the final query or via ChangeTracker.

There is one thing to note though, which is not explained in the documentation. If the query expression tree contains more than one AsNoTracking / AsTracking calls, the last call takes precedence. Which means that by adding AsNoTracking or if you add AsTracking to the final query will control it's behavior regardless of the any inner tracking behavior calls or ChangeTracker property.

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