根据依赖键清除缓存

Question

基于日期时间值，我将值插入缓存：

Dim Value1 As String = "value1"
Dim Value2 As String = "value2"
Dim Key1 As String = "Key" & New Date(2014, 1, 1, 1, 1, 0).ToString
Dim Key2 As String = "Key" & New Date(2014, 1, 1, 1, 2, 0).ToString
HttpContext.Current.Cache.Insert(Key1, Value1)
HttpContext.Current.Cache.Insert(Key2, Value2)

是否可以使用另一个缓存项作为 CacheDependency 使这些缓存项失效？

我尝试了以下方法，但这不起作用：

Dim Keys As String() = New String(0) {}
Keys(0) = "OtherKey"
Dim MyDependency As New System.Web.Caching.CacheDependency(Nothing, Keys)
HttpContext.Current.Cache.Insert(Key1, Value1, MyDependency)
HttpContext.Current.Cache.Insert(Key2, Value2, MyDependency)

'To clear all cache items:
HttpContext.Current.Cache.Remove("OtherKey")

当我使用它（没有删除语句）时，永远无法在缓存中找到这些项目。我在这里做错了什么？

Answer 1

如果您想将 CacheDependency 用于另一个缓存键：

• 您所依赖的密钥（即OtherKey）必须在缓存中找到（参见this article）。否则将无法在缓存中找到您的项目。
• 您需要为每个项目创建不同的 CacheDependency 实例。否则会报错An attempt was made to reference a CacheDependency object from more than one Cache entry（见this question的答案）

所以你插入项目的代码是这样的：

' Make sure OtherKey is found in the cache
HttpContext.Current.Cache.Insert("OtherKey", "SomeValue")

' Add the items with a different CacheDependency instance per item
Dim Keys As String() = New String(0) {}
Keys(0) = "OtherKey"
HttpContext.Current.Cache.Insert(Key1, Value1, New System.Web.Caching.CacheDependency(Nothing, Keys))
HttpContext.Current.Cache.Insert(Key2, Value2, New System.Web.Caching.CacheDependency(Nothing, Keys))

• 请注意，如果您不添加键为 OtherKey 的缓存项，将永远找不到依赖项。

那么当你从缓存中移除OtherKey时，依赖项会被自动移除。所以这一行会自动从缓存中删除 Key1 和 Key2：

HttpContext.Current.Cache.Remove("OtherKey")

希望对你有帮助！