问题
Aim to achieve : Want to dump a fetched table to a excel sheet.
My implementation :
Imports System.Data.OleDb
Private Sub getRawDataNextMonth()
Dim sheetName As String = "RawData"
Dim con As New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\rawData.xlsx;Extended Properties=""Excel 12.0 XML;""")
Dim adapter As New Data.OleDb.OleDbDataAdapter("SELECT * FROM [Sheet1$]", con)
Dim dataSet As New Data.DataSet
adapter.Fill(dataSet)
Dim dataTable As Data.DataTable = dataSet.Tables(0)
Dim rawData(dataTable.Rows.Count, dataTable.Columns.Count - 1) As Object
Dim range As Excel.Range = WB.Sheets(sheetName).Range("A2:T" + dataTable.Rows.Count.ToString())
For col = 0 To dataTable.Columns.Count - 1
For row = 0 To dataTable.Rows.Count - 1
rawData(row, col) = dataTable.Rows(row).ItemArray(col)
Next
Next
range.Value2 = rawData
End Sub
I am new to data fetching and ADO.Net concepts and just got it working. But..
This seems to be very inefficient and lame to me.
So, can you help reducing the complexity and may be improve performance ?
A totally different (Better) implementation is most welcome !
Please help me optimize this... with your experience !
回答1:
This function writes out to a text file as CSV format and then opens the file in Excel and saves it as xlsx format. I tried this with a 53 column x 10,000 row table and it took ~2 seconds:
Private Sub Export3(ByVal filename As String, ByRef dt As DataTable)
Dim tempfile As String = Path.GetTempPath + Path.GetFileNameWithoutExtension(Path.GetTempFileName) + ".csv"
Dim sb As StringBuilder
Using sw As StreamWriter = New StreamWriter(tempfile)
sb = New StringBuilder("")
For c As Integer = 0 To dt.Columns.Count - 1
sb.Append(dt.Columns(c).ColumnName + ",")
Next
sw.WriteLine(sb.ToString.TrimEnd(","c))
For r As Integer = 0 To dt.Rows.Count - 1
sb = New StringBuilder("")
For c As Integer = 0 To dt.Columns.Count - 1
sb.Append(dt.Rows(r).Item(c).ToString + ",")
Next
sw.WriteLine(sb.ToString.TrimEnd(","c))
Next
End Using
Dim xlApp As Excel.Application = Nothing
Dim xlBook As Excel.Workbook = Nothing
Try
xlApp = New Excel.Application
'xlApp.Visible = True 'for debugging
xlApp.DisplayAlerts = False
xlBook = xlApp.Workbooks.Open(tempfile)
xlBook.SaveAs(filename, Excel.XlFileFormat.xlWorkbookDefault)
My.Computer.FileSystem.DeleteFile(tempfile)
Finally
If Not IsNothing(xlBook) Then
xlBook.Close()
End If
If Not IsNothing(xlApp) Then xlApp.Quit()
End Try
End Sub
来源:https://stackoverflow.com/questions/6855959/how-to-optimize-this-simple-but-complex-looking-implementation-in-vb-net