<Item time="2016-01-11T05:39:01" page="/fr/iconic-bright-cushion-spf-50-pa-nude-perfection-compact-foundation/p/5490/c/30"

url="http://www.shopunt.com/fr/iconic-bright-cushion-spf-50-pa-nude-perfection-compact-foundation/p/5490/c/30?utm_source=edm&amp;utm_medium=email&amp;utm_content=20160107_cushion_4&amp;utm_campaign=makeup&amp;OutAD_Id=5825" username="Not Member" browserName="Chrome" browserVersion="34.0" userAgent="Mozilla/5.0 (Linux; Android 5.1.1; SAMSUNG SM-N915FY Build/LMY47X) AppleWebKit/537.36 (KHTML, like Gecko) SamsungBrowser/2.1 Chrome/34.0.1847.76 Mobile Safari/537.36" RemoteIP="37.160.206.7" Ref="No Ref" RequestType="GET" Ver="3">

    <ErrMsg>

    </ErrMsg>

    <ErrStack> 於 System.Web.CachedPathData.ValidatePath(String physicalPath)

於 System.Web.HttpApplication.PipelineStepManager.ValidateHelper(HttpContext context)</ErrStack>

    <Post>

    </Post>

    <Cookie>

    </Cookie>

</Item>

網站開發，善用 Cached DataTable 可以使網站效能倍增，不必一直去資料庫抓資料。
但是使用 Cached DataTable 有一個地方要注意
就是他是 Shared 物件，表示同時有好幾個頁面都可以存取他

例如A網頁將資料抓出，然後變更裡面的DataRow資料，
另一個B網頁也會跟著變更

由於 Cached DataTable 在 Set DataRow Value 時
可能 Critical Section 沒有處理好，若真的同時多個thread 操作
會出現 Exception
(System.ArgumentOutOfRangeException: 索引超出範圍。必須為非負數且小於集合的大小。)

建議:

• Cached DataTable 最好是只能用來讀，不要Set Value
• 若需要Set Value，可以使用 DataTable Copy()功能，先複製出來再操作，就不會影響到原始資料

            '這是 UNT FixPage 物件抓取單一資料的範例

            Shared Function GetSpecialPage2FromCachedDT(ByVal Key As Int32) As DB.SpecialPage2

                Dim DT As DataTable = GetAllDataFromBaseTableWithCache()

                Dim Row As DataRow = DT.Rows.Find(Key)

                If Row IsNot Nothing Then

                    '避免每個thread都共用table 寫入資料會出現問題

                    Dim newDT As DataTable = DT.Clone()

                    newDT.ImportRow(Row)

                    Return New SpecialPage2(newDT.Rows(0))

                Else

                    Return Nothing

                End If

            End Function

<link href="圖片連結網址" rel="image_src" type="image/jpeg">

Response.Cache.SetCacheability(HttpCacheability.Private)

Response.Cache.SetExpires(Now.AddYears(1))  '一年後才會到期，沒有這個就不會有 200 (From Cache)

Response.Cache.SetLastModified(Now)  '若是 Browser 送出了一個新的 Request, 有可能會回 304

        

'更新

        If UW.WU.IsNonEmptyFromQueryStringOrForm("Refresh") Then

            System.Web.HttpContext.Current.Cache.Remove(CacheName)

        End If

        '快取部分

        If obj Is Nothing Then

            Dim SQL As String = ""

            SQL = "select * from Product with (nolock)"

            obj = UW.SQL.DTFromSQL(SQL)



            Dim AC As New AggregateCacheDependency



            Dim DepArray() As CacheDependency = { _

                 New SqlCacheDependency(UW.SQL.sqlCacheDependencyName, "Product"), _

                 New SqlCacheDependency(UW.SQL.sqlCacheDependencyName, "Product_Category") _

            }



            AC.Add(DepArray)

            Dim FD As New CacheDependency(UW.Template.TemplateRoot & "2013UI\Product\DirectBuyAllProduct.html")

            AC.Add(FD)



            System.Web.HttpContext.Current.Cache.Insert(CacheName, obj, AC)



        End If

DT.Select("Id=" & ProductId) 

'寫入Cache前先設定好

DT.PrimaryKey = New DataColumn() {obj.Columns("Id")} 

Dim row As DataRow = DT.Rows.Find(ProductId)