今天發現 uw.mail.sendmail 在寄信時，若是有附件，附件會被鎖住，直到下一次有人寄件信為止。

解決方法是一要把 System.Net.Mail.MailMessage 物件釋放掉 (做 dispose 的動做)。要記得更新 sendmail 這支程式哦。

有點笨的問題, 但每次遇到都忘了要怎麼定義字串陣列 :P 在這裡記錄一下.. 以下的 HT 是一個 Hashtable

Dim arrKeys(HT.Count - 1) As String

HT.Keys.CopyTo(arrKeys, 0)

VB 不知何時多了一個 if 函式, 可以用來取代 iif.

使用 iif 時, true part 和 false part 都會執行.

改用 if 就不會有這個問題, 比較像 AndAlso 和 OrElse 的行為. 有短路（short circuit）的特性. 會依據判斷式的結果只執行部份的結果.

IIf(X IsNot Nothing, X.qty, 0) --> 會有 Error



If(X IsNot Nothing, X.qty, 0) --> OK

2012/6/3 補述:
發現一個問題, 在 VS2010 中, If(X IsNot Nothing, X.qty, 0) 會造成 Compile 錯誤, 但網站是可以正常執行的..

這是 VS2010 的 Bug 嗎 ?

主要是使用 Printing.PreviewPrintController 的產生預覽圖片的功能來儲存列印內容, 再把圖片送到印表機, 以保証列印內容和儲存的圖檔是一致的. 值得一提的是, 在預覽時可以使用不同的印表機, 以便讓產生較小的圖檔, 否則有時會發生 GDI+ 的錯誤.

Sample 如下:

Imports System.Drawing.Printing

Namespace X

    Partial Public Class PrintSomething

        Dim PD As PrintDocument

        Dim ppc As New Printing.PreviewPrintController()

        Dim TotalPage As Int32 = 0

        ''' <summary>

        ''' 第幾次列印, 用來控制寫出的圖檔

        ''' </summary>

        ''' <remarks></remarks>

        Dim PrintCount As Int32 = 1

        Dim PageCount As Int32 = 1

            :

            :

            :

      

        Sub New(ByVal oPM As DB.PackingListMain, ByVal dtDetail As DataTable, dtUsedCoupon As DataTable)

            '初始化資料

            :

            :

            :

        End Sub

        Sub InitPrintDocument()

            '在這裡設定 PrintDocument 的紙張, 印表機, 邊界, 橫印或直印

            PD = New PrintDocument

            :

            :

            :

        End Sub

        Sub print()

            InitPrintDocument()

            PD.PrintController = ppc

           

            ' 第一次先把列印結果存在 Printing.PreviewPrintController 中

            AddHandler PD.PrintPage, AddressOf GeneratePreview

            '再來儲存圖片

            AddHandler PD.EndPrint, AddressOf SaveImage

            PD.Print()

        End Sub



        Dim ppi() As Printing.PreviewPageInfo

        Dim PrintPage As Int32 = 0

        Sub SaveImage(ByVal sender As Object, ByVal ev As PrintEventArgs)

            PrintDebug("Save Image Start, " & Now.ToString("yyyy-MM-dd HH:mm:ss.fff"))

            '把圖檔存起來

            Dim TF As String = Now.ToString("yyyyMMddHHmmss") ' DB.SysConfig.Path.LocalDataRoot

            Dim PathLocal As String = "C:\PrintLog\" & TF.Substring(0, 4) & "-" & TF.Substring(4, 2) & "\"

            Dim PathPackingListSheetImage As String = DB.SysConfig.PackingListSheetImage & TF.Substring(0, 4) & "-" & TF.Substring(4, 2) & "\"

            System.IO.Directory.CreateDirectory(PathLocal)

            System.IO.Directory.CreateDirectory(PathPackingListSheetImage)

            Dim LatestImages As String = ""

            ppi = ppc.GetPreviewPageInfo()

            For x As Integer = 0 To ppi.Length - 1

                Dim Filename As String = TF & "_" & Me.oPM.Id & "_" & x & ".png"

                ppi(x).Image.Save(PathLocal & Filename, System.Drawing.Imaging.ImageFormat.Png)

            Next



            '把圖檔印出來

            For x As Integer = 0 To ppi.Length - 1

  '建立新的 PrintDocument

                InitPrintDocument()

                If CST.WebConfig.Server_NAME = "測試主機" Then

                    UW.WU.DebugWriteLine("PrinterName: " & Me.PD.PrinterSettings.PrinterName)

                    UW.WU.DebugWriteLine("PaperSize: " & PD.DefaultPageSettings.PaperSize.PaperName)

                    PD.DocumentName = "PackingList"

                    PD.PrinterSettings.PrintFileName = "C:\PDF\PackingList" & Now.ToString("yyyyMMddHHmmss") & "_" & PrintPage & ".prn"

                    PD.PrinterSettings.PrintToFile = True

                    'PD.PrinterSettings.

                End If

                '很奇怪, 這裡不會分頁, 所以要一張一張印   

                AddHandler PD.PrintPage, AddressOf pd_PrintPage2

                PD.Print()



               PrintPage += 1

            Next

        End Sub

        Private Sub pd_PrintPage2(ByVal sender As Object, ByVal ev As PrintPageEventArgs)

            '很奇怪, 這裡不會分頁, 所以要一張一張印           

            ev.Graphics.DrawImage(ppi(PrintPage).Image, 0, 0)

            ev.HasMorePages = False

        End Sub



        Private Sub GeneratePreview(ByVal sender As Object, ByVal ev As PrintPageEventArgs)

            ' 列印內容

        End Sub

        End Class

    End Class

End Namespace

在 Select 指令後, 依據結果做一些工作, 即使有 Transaction, 但還是有可能發生一致性的問題:

Ex:

        Dim Conn As SqlConnection = UW.SQL.GetOpenedConnection

        Dim Tran As SqlTransaction = Conn.BeginTransaction

        Try

            Dim C As Int32 = UW.SQL.GetSingleValue("Select Counter From TableA Where Id = 1", Tran)

            C = C + 1

            UW.SQL.executeSQL("Update TableA Set Counter = " & C & " Where  Id = 1", Tran)

            Tran.Commit()

        Catch ex As Exception

            Tran.Rollback()

            UW.WU.DebugWriteLine(ex.ToString, True, True)

        Finally

            If Conn.State <> ConnectionState.Closed Then

                Conn.Close()

            End If

        End Try

以上的程式由兩個 Session 同時執行時, 並不能保証 Counter 會被加 2

若是要保証兩個 Session 都會把 Counter 加一(總共加 2), 要把以下這一行

Dim C As Int32 = UW.SQL.GetSingleValue("Select Counter From TableA Where Id = 1", Tran)

改為

Dim C As Int32 = UW.SQL.GetSingleValue("Select Counter From TableA With(XLock) Where Id = 1", Tran)