WinForms应用程序数据缓存-缓存在哪一层?

我们的数据每晚都会在与我的应用程序数据库位于同一实例中的数据库中更新。因此,为了节省数据库调用,我想将这个静态的当日数据缓存到List(Of MyObject)中。从理论角度来看,这个缓存的List(of)是否应该通过全局变量缓存在表示层代码中?它是否应该在中的全局变量中。DLL?

Public Shared Function Search(ByVal criteria As Core.Other.Customer) As List(Of Core.Other.Customer)
    ' TODO: Check the customer cache to see if it has been populated yet. If not, populate it.
    If 1 = 1 Then
        ' TODO: Variable "list" needs to be a global object in the DLL.
        ' For SO readers: Dal class declared Friend.
        Dim list As List(Of Core.Other.Customer) = Dal.Search.Customers.GetCache()
    End If

    Dim results As New List(Of Core.Other.Customer)
    ' TODO: Find the relevant customers in the cache and add them to variable "results".
    Return results
End Function

这是我能做到的最好的方式吗?