Fast Export of Large Datatable to Excel Spreadsheet in VB.Net - vb.net

Question

I have an interesting conundrum here, how do I quickly (under 1 minute) export a large datatable (filled from SQL, 35,000 rows) into an Excel spreadsheet for users. I have code in place that can handle the export, and while nothing is "wrong" with the code per se, it is infuriatingly slow taking 4 minutes to export the entire file (sometimes longer if a user has less RAM or is running more on their system). Sadly, this is an improvement over the 10+ minutes it used to take using our old method. Simply put, can this be made any faster, without using 3rd party components? If so, how? My code is as follows, the slow down occurs between messageboxes 6 and 7 where each row is written. Thank you all for taking the time to take a look at this:
Private Sub btnTest_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnJeffTest.Click
Test(MySPtoExport)
End Sub
Private Sub Test(ByVal SQL As String)
'Declare variables used to execute the VUE Export stored procedure
MsgBox("start stop watch")
Dim ConnectionString As New SqlConnection(CType(ConfigurationManager.AppSettings("ConnString"), String))
Dim cmdSP As New SqlClient.SqlCommand
Dim MyParam As New SqlClient.SqlParameter
Dim MyDataAdapter As New SqlClient.SqlDataAdapter
Dim ExportDataSet As New DataTable
Dim FilePath As String
MsgBox("stop 1 - end of declare")
Try
' open the connection
ConnectionString.Open()
' Use the connection for this sql command
cmdSP.Connection = ConnectionString
'set this command as a stored procedure command
cmdSP.CommandType = CommandType.StoredProcedure
'get the stored procedure name and plug it in
cmdSP.CommandText = SQL
'Add the Start Date parameter if required
Select Case StDt
Case Nothing
' there's no parameter to add
Case Is = 0
' there's no parameter to add
Case Else
'add the parameter name, it's direction and its value
MyParam = cmdSP.Parameters.Add("#StartDate", SqlDbType.VarChar)
MyParam.Direction = ParameterDirection.Input
MyParam.Value = Me.txtStartDate.Text
End Select
MsgBox("stop 2 - sql ready")
'Add the End Date parameter if required
Select Case EdDt
Case Nothing
' there's no parameter to add
Case Is = 0
' there's no parameter to add
Case Else
'add the parameter name, it's direction and its value
MyParam = cmdSP.Parameters.Add("#EndDate", SqlDbType.VarChar)
MyParam.Direction = ParameterDirection.Input
MyParam.Value = Me.txtEndDate.Text
End Select
'Add the single parameter 1 parameter if required
Select Case SPar1
Case Is = Nothing
' there's no parameter to add
Case Is = ""
' there's no parameter to add
Case Else
'add the parameter name, it's direction and its value
MyParam = cmdSP.Parameters.Add(SPar1, SqlDbType.VarChar)
MyParam.Direction = ParameterDirection.Input
MyParam.Value = Me.txtSingleReportCrt1.Text
End Select
'Add the single parameter 2 parameter if required
Select Case Spar2
Case Is = Nothing
' there's no parameter to add
Case Is = ""
' there's no parameter to add
Case Else
'add the parameter name, it's direction and its value
MyParam = cmdSP.Parameters.Add(Spar2, SqlDbType.VarChar)
MyParam.Direction = ParameterDirection.Input
MyParam.Value = Me.txtSingleReportCrt2.Text
End Select
MsgBox("stop 3 - params ready")
'Prepare the data adapter with the selected command
MyDataAdapter.SelectCommand = cmdSP
' Set the accept changes during fill to false for the NYPDA export
MyDataAdapter.AcceptChangesDuringFill = False
'Fill the Dataset tables (Table 0 = Exam Eligibilities, Table 1 = Candidates Demographics)
MyDataAdapter.Fill(ExportDataSet)
'Close the connection
ConnectionString.Close()
'refresh the destination path in case they changed it
SPDestination = txtPDFDestination.Text
MsgBox("stop 4 - procedure ran, datatable filled")
Select Case ExcelFile
Case True
FilePath = SPDestination & lblReportName.Text & ".xls"
Dim _excel As New Microsoft.Office.Interop.Excel.Application
Dim wBook As Microsoft.Office.Interop.Excel.Workbook
Dim wSheet As Microsoft.Office.Interop.Excel.Worksheet
wBook = _excel.Workbooks.Add()
wSheet = wBook.ActiveSheet()
Dim dt As System.Data.DataTable = ExportDataSet
Dim dc As System.Data.DataColumn
Dim dr As System.Data.DataRow
Dim colIndex As Integer = 0
Dim rowIndex As Integer = 0
MsgBox("stop 5 - excel stuff declared")
For Each dc In dt.Columns
colIndex = colIndex + 1
_excel.Cells(1, colIndex) = dc.ColumnName
Next
MsgBox("stop 6 - Header written")
For Each dr In dt.Rows
rowIndex = rowIndex + 1
colIndex = 0
For Each dc In dt.Columns
colIndex = colIndex + 1
_excel.Cells(rowIndex + 1, colIndex) = dr(dc.ColumnName)
Next
Next
MsgBox("stop 7 - rows written")
wSheet.Columns.AutoFit()
MsgBox("stop 8 - autofit complete")
Dim strFileName = SPDestination & lblReportName.Text & ".xls"
If System.IO.File.Exists(strFileName) Then
System.IO.File.Delete(strFileName)
End If
MsgBox("stop 9 - file checked")
wBook.SaveAs(strFileName)
wBook.Close()
_excel.Quit()
End Select
MsgBox("File " & lblReportName.Text & " Exported Successfully!")
'Dispose of unneeded objects
MyDataAdapter.Dispose()
ExportDataSet.Dispose()
StDt = Nothing
EdDt = Nothing
SPar1 = Nothing
Spar2 = Nothing
MyParam = Nothing
cmdSP.Dispose()
cmdSP = Nothing
MyDataAdapter = Nothing
ExportDataSet = Nothing
Catch ex As Exception
' Something went terribly wrong. Warn user.
MessageBox.Show("Error: " & ex.Message, "Stored Procedure Running Process ", _
MessageBoxButtons.OK, MessageBoxIcon.Error)
Finally
'close the connection in case is still open
If Not ConnectionString.State = ConnectionState.Closed Then
ConnectionString.Close()
ConnectionString = Nothing
End If
' reset the fields
ResetFields()
End Try
End Sub

Answer 1

Even though the question was asked several years ago, I thought I would add my solution since the question was posed in VB and the "best answer" is in C#. This solution writes 22,000+ rows (1.9MB) in 4 seconds on an i7 System w/ 16GB RAM.
Imports Excel = Microsoft.Office.Interop.Excel
Public Class Main
Private Sub btnExportToExcel(sender As Object, e As EventArgs) Handles btnExpToExcel.Click
'Needed for the Excel Workbook/WorkSheet(s)
Dim app As New Excel.Application
Dim wb As Excel.Workbook = app.Workbooks.Add()
Dim ws As Excel.Worksheet
Dim strFN as String = "MyFileName.xlsx" 'must have ".xlsx" extension
'Standard code for filling a DataTable from SQL Server
Dim strSQL As String = "My SQL Statement for the DataTable"
Dim conn As New SqlConnection With {.ConnectionString = "My Connection"}
Dim MyTable As New DataTable
Dim cmd As New SqlCommand(strSQL, conn)
Dim da As New SqlDataAdapter(cmd)
da.Fill(MyTable)
'Add a sheet to the workbook and fill it with data from MyTable
'You could create multiple tables and add additional sheets in a loop
ws = wb.Sheets.Add(After:=wb.Sheets(wb.Sheets.Count))
DataTableToExcel(MyTable, ws, strSym)
wb.SaveAs(strFN) 'save and close the WorkBook
wb.Close()
MsgBox("Export complete.")
End Sub
Private Sub DataTableToExcel(dt As DataTable, ws As Excel.Worksheet, TabName As String)
Dim arr(dt.Rows.Count, dt.Columns.Count) As Object
Dim r As Int32, c As Int32
'copy the datatable to an array
For r = 0 To dt.Rows.Count - 1
For c = 0 To dt.Columns.Count - 1
arr(r, c) = dt.Rows(r).Item(c)
Next
Next
ws.Name = TabName 'name the worksheet
'add the column headers starting in A1
c = 0
For Each column As DataColumn In dt.Columns
ws.Cells(1, c + 1) = column.ColumnName
c += 1
Next
'add the data starting in cell A2
ws.Range(ws.Cells(2, 1), ws.Cells(dt.Rows.Count, dt.Columns.Count)).Value = arr
End Sub
End Class
Hope it helps.

Answer 2

As when using VBA to automate Excel, you can assign an array directly to the value of a Range object: this is done as a single operation, so you remove the overhead associated with making multiple calls across the process boundaries between your .Net code and the Excel instance.
Eg, see the accepted answer here: Write Array to Excel Range

Answer 3

The answer from CPRouse worked for me except that it left off the last row of data. In the Private Sub DataTableToExcel function, I added 1 to the rows.count on this line and it wrote all the records. ws.Range(ws.Cells(2, 1), ws.Cells(dt.Rows.Count + 1, dt.Columns.Count)).Value = arr

Answer 4

Here is a piece of my own code that performs a very fast export of data from a DataTable to an Excel sheet (use the "Stopwatch" object to compare the speed and let me a comment):
Dim _excel As New Excel.Application
Dim wBook As Excel.Workbook
Dim wSheet As Excel.Worksheet
wBook = _excel.Workbooks.Add()
wSheet = wBook.ActiveSheet()
Dim dc As System.Data.DataColumn
Dim colIndex As Integer = 0
Dim rowIndex As Integer = 0
'Nombre de mesures
Dim Nbligne As Integer = DtMesures.Rows.Count
'Ecriture des entêtes de colonne et des mesures
'(Write column headers and data)
For Each dc In DtMesures.Columns
colIndex = colIndex + 1
'Entête de colonnes (column headers)
wSheet.Cells(1, colIndex) = dc.ColumnName
'Données(data)
'You can use CDbl instead of Cobj If your data is of type Double
wSheet.Cells(2, colIndex).Resize(Nbligne, ).Value = _excel.Application.transpose(DtMesures.Rows.OfType(Of DataRow)().[Select](Function(k) CObj(k(dc.ColumnName))).ToArray())
Next

Answer 5

We had a VB.NET app that did exactly this, and took even longer for our users who were on slow PC's... sometimes 15 minutes.
The app is now an ASP/VB.NET app which simply builds an HTML table and outputs the result as an .xls extension... excel is able to read the HTML table and parse it into a grid format. You can still pass in XML for formatting and options, horizontal pane locking, etc.
If you don't have the option of using ASP.NET... try looking into a way to build an HTML table string and have excel parse & populate for you... much faster! I'm sure excel can parse other types as well.... XML, Arrays, HTML, etc... all would be quicker than manually building each row through VB.NET objects.