Object references and cache

I have a function GetAllProducts() which fetches all products from a database and stores it in the cache for future requests. This works fine, but if I then call the function e.g. ProductSearchResults = GetAllProducts(), and then modify ProductSearchResults variable, this also modifies the cache, which is very important this never happens, as the cache affects the whole website.

I understand this开发者_高级运维 is because both ProductSearchResults and the cache now have the same reference, but how do I solve the problem? Is there something that I can put in GetAllProducts() to ensure the cache always uses its own value?

 Public Shared Function GetAllProducts() As ProductCollection

        Dim Products As New ProductCollection()

        If IsNothing(System.Web.HttpContext.Current.Cache("ProductData")) Then

            '////// Database code to get products goes here //////

            System.Web.HttpContext.Current.Cache.Insert("ProductData", Products, Nothing, DateTime.Now.AddMinutes(5), TimeSpan.Zero)
        End If
        Products = System.Web.HttpContext.Current.Cache("ProductData")

        Return Products

    End Function

 Public Shared Function SearchProducts(ByVal SearchText As String) As ProductCollection

        Dim ProductSearchResults As ProductCollection = Nothing

        If SearchText <> "" Then

            SearchText = SearchText.ToLower()

            Dim Keywords As New ArrayList()
            Keywords.AddRange(SearchText.Split(" ".ToCharArray(), StringSplitOptions.RemoveEmptyEntries))

            ProductSearchResults = GetAllProducts()

            For i As Integer = 0 To Keywords.Count - 1

                For j As Integer = ProductSearchResults.Count - 1 To 0 Step -1
                    If ProductSearchResults(j).ProductName.ToLower.Contains(Keywords(i)) = False Then
                        ProductSearchResults.RemoveAt(j)
                    End If
                Next

            Next

        End If

        Return ProductSearchResults

    End Function

This is because you are essentially returning a collection of pointers to the object thats in the cache. You could implement IClonable on your object and have a Function that returns a new collection with cloned objects.

Public Function GetClonedObjects() As ProductCollection

Dim myCollection As New List(Of MyObject)

For Each item as Product in GetProducts()
   myCollection.Add(item.Clone)
Loop

Return myCollection

End Function

Or Create a property to hold a cloned copy of the collection

    Private _clonedProducts As ProductCollection = Nothing
    Public ReadOnly Property ClonedProducts As ProductCollection
      Get
        If _clonedProducts Is Nothing Then
          _clonedProducts = New ProductCollection
          For Each item As Product In GetAllProducts()
            _clonedProducts.Add(item.Clone())
          Next
        End If
        Return _clonedProducts
      End Get
    End Property