vb.net - 如何使用 VistaDB 进行数据库备份？

Question

我正在尝试使用 VistaDB 对数据库进行 XML 导出。不幸的是，我迷路了。

到目前为止，这是我的代码：

    Dim instance As IVistaDBDatabase
    Dim value As System.Int64

    SaveFileDialog2.InitialDirectory = "C:\"
    Select Case SaveFileDialog2.ShowDialog()
        Case Windows.Forms.DialogResult.OK
            Try
                instance.ExportXml(SaveFileDialog2.FileName, VistaDBXmlWriteMode.All)
            Catch ex As Exception
                MsgBox(ex.ToString)
            End Try
    End Select

我得到的只是对象未设置为对象的实例（或类似的东西）。

任何人都可以提供这样的指导吗？

Answer 1

在旧代码包的帮助下，我能够弄清楚。这是正确的代码：

    Dim vdbDatabase As IVistaDBDatabase = Nothing
    Dim filenameDB As String = SaveFileDialog2.FileName
    Dim filenameXML As String = SaveFileDialog2.FileName

    Select Case SaveFileDialog2.ShowDialog()
        Case System.Windows.Forms.DialogResult.OK
            Try

                ' Call the method that will open the connection to the database and return an open IVistaDBDatabase object for the database to us
                vdbDatabase = DDA.VistaDBEngine.Connections.OpenDDA.OpenDatabase("C:\Ledger.vdb5", VistaDBDatabaseOpenMode.NonexclusiveReadOnly, Nothing)


                ' Clear the XML Transfer List - this is the list used by the Import/Export methods
                vdbDatabase.ClearXmlTransferList()

                ' Loop through the tables in the database and add them to the XmlTransferList
                For Each tableName As String In vdbDatabase.GetTableNames()
                    vdbDatabase.AddToXmlTransferList(tableName)
                Next


                ' Call the ExportXML method with the name of the XML      file and the WriteMode value indicating what to Export
                vdbDatabase.ExportXml(filenameXML, VistaDBXmlWriteMode.All)

                ' If the database is open - close it
                If Not vdbDatabase.IsClosed Then
                    vdbDatabase.Close()
                End If
                MsgBox("Database Export complete.", MsgBoxStyle.Information)
            Catch ex As Exception
                WriteErrorEvent("Error exporting Database in addin", ex)
                MsgBox("An error occured attempting to export the Database. Error Message:" & vbCrLf & vbCrLf & ex.ToString, MsgBoxStyle.Exclamation)
            Finally
                ' If we have a vdbDatabase object               
                If Not (vdbDatabase Is Nothing) Then
                    ' If it is open, close it
                    If Not vdbDatabase.IsClosed Then
                        vdbDatabase.Close()
                    End If

                    ' Dispose of the object
                    vdbDatabase.Dispose()
                End If
            End Try
    End Select

Answer 2

有点晚了，但我对你的代码做了一些小改动，所以你可以看到备份的确切时间。

    Dim vdbDatabase As IVistaDBDatabase = Nothing
    Dim filenamedb As String = vdbDatabase
    Dim filenameXML As String = "MyDataBaseName_" + Now.ToString("dd-MM-yyyy_hh-mm-ss") + ".Xml"
    Dim path As String
    path = System.IO.Path.GetFullPath(filenameXML)

    Try
   vdbDatabase = DDA.VistaDBEngine.Connections.OpenDDA.OpenDatabase("DataDirectory|MyDataBase.vdb5", VistaDBDatabaseOpenMode.NonexclusiveReadOnly, Nothing)
vdbDatabase.ClearXmlTransferList()

        For Each tableName As String In vdbDatabase.GetTableNames()
            vdbDatabase.AddToXmlTransferList(tableName)
        Next

        vdbDatabase.ExportXml(filenameXML, VistaDBXmlWriteMode.All)

        If Not vdbDatabase.IsClosed Then
            vdbDatabase.Close()
        End If

        MsgBox("Backup is in " + path, MsgBoxStyle.Information)

    Catch ex As Exception
        MsgBox("An error occured attempting to export the Database. Error Message:" & vbCrLf & vbCrLf & ex.ToString, MsgBoxStyle.Exclamation)
    Finally

        If Not (vdbDatabase Is Nothing) Then
            If Not vdbDatabase.IsClosed Then
                vdbDatabase.Close()
            End If               
            vdbDatabase.Dispose()
        End If
    End Try