In my WPF
application, I have a huge data table (System.Data.DataTable
) that I need to write to a sheet in an Excel document. This is the heavy part of the function:
for (; i < dt.Rows.Count; i++)
{
for (int colNum = 0; colNum < dt.Columns.Count; colNum++)
newSheet.Cells[i + rowNumber, colNum + 1] = dt.Rows[i][colNum].ToString();
applyRowBorderStyle(newSheet, i + rowNumber, dt.Columns.Count);
}
dt is the DataTable
, newSheet
is the Excel sheet I write to, and applyRowBorderStyle()
adds borders to all the cells in the row. It runs very slowly when the data table is big, taking 10 minutes or even longer. Is there any way to make it run faster?
Edit: The program analyses a lot of data and makes a lot of sheets, and I can't make the user do anything differently. I must use only Microsoft Excel. This sheet's table always has 42 columns, but the number of rows varies according to how much data the program receives, approximately 500 lines. "applyRowBorderStyle" will make the code run a bit faster, but doesn't meet the requirements. I really hope there is another way to make it run faster.
On the External Data tab, in the Export group, click Excel. In the Export - Excel Spreadsheet dialog box, review the suggested file name for the Excel workbook (Access uses the name of the source object). If you want, you can modify the file name. In the File Format box, select the file format that you want.
Enable Fast Data Load in Power Query If your queries are slow, you can enable the fast data load option to speed them up. Go to the Data tab and press the Get Data button, then open the Query Options. Go to the Global Data Load settings and check the Fast Data Load box.
The way to reduce the file size and memory requirements of a data model is to reduce the overall number of columns and rows, and the number of unique values appearing in each column. Here are some techniques we covered: Removing columns is of course the best way to save space. Decide which columns you really need.
found the answer! here's the function iv'e wrote, and the reference I used: http://www.codeproject.com/Articles/21519/Fast-Exporting-from-DataSet-to-Excel
using System.Data;
using Excel = Microsoft.Office.Interop.Excel;
private void FastDtToExcel(DataTable dt, Excel.Worksheet sheet, int firstRow, int firstCol, int lastRow, int lastCol)
{
Excel.Range top = sheet.Cells[firstRow, firstCol];
Excel.Range bottom = sheet.Cells[lastRow, lastCol];
Excel.Range all = (Range)sheet.get_Range(top, bottom);
string[,] arrayDT = new string[dt.Rows.Count, dt.Columns.Count];
//loop rows and columns
for (int i = 0; i < dt.Rows.Count; i++)
for (int j = 0; j < dt.Columns.Count; j++)
arrayDT[i, j] = dt.Rows[i][j].ToString();
//insert value in worksheet
all.Value2 = arrayDT;
}
takes less than a second, which is awesome :)
I've always found the most efficient way to get a datatable to excel is to convert the datatable to a adodb.recordset.
The important piece is using excels CopyFromRecordSet Method
objWorksheet.Range("A1").CopyFromRecordset(ConvertToRecordset(dt))
Just ran a couple comparisons and below are the results.
50k records
Datatable to excel = 1 minutes 6 seconds
Datatable to RS to Excel = 2 seconds
250k records
Datatable to excel = 5 minutes 29 seconds
Datatable to RS to Excel = 10 seconds
The below is obviously written in vb.net so you'll need to convert the code to C# for your application but hope it helps.
Public Class Form1
Private dt As New DataTable
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
dt.Columns.Add("header1")
dt.Columns.Add("header2")
dt.Columns.Add("header3")
dt.Columns.Add("header4")
For i = 0 To 250000
dt.Rows.Add({i, i, i, i})
Next
End Sub
Private Sub DataTableConvBtn_Click(sender As System.Object, e As System.EventArgs) Handles DataTableConvBtn.Click
Dim starttime = Now.ToString
Dim objExcel = CreateObject("Excel.Application")
objExcel.Visible = True
Dim objWorkbook = objExcel.Workbooks.Add()
Dim objWorksheet = objWorkbook.Worksheets(1)
objWorksheet.Range("A1").CopyFromRecordset(ConvertToRecordset(dt))
Dim endtime = Now.ToString
MsgBox(starttime & vbCrLf & endtime)
End Sub
Public Shared Function ConvertToRecordset(ByVal inTable As DataTable) As ADODB.Recordset
Dim result As ADODB.Recordset = New ADODB.Recordset()
result.CursorLocation = ADODB.CursorLocationEnum.adUseClient
Dim resultFields As ADODB.Fields = result.Fields
Dim inColumns As System.Data.DataColumnCollection = inTable.Columns
For Each inColumn As DataColumn In inColumns
resultFields.Append(inColumn.ColumnName, TranslateType(inColumn.DataType), inColumn.MaxLength, ADODB.FieldAttributeEnum.adFldIsNullable, Nothing)
Next
result.Open(System.Reflection.Missing.Value, System.Reflection.Missing.Value, ADODB.CursorTypeEnum.adOpenStatic, ADODB.LockTypeEnum.adLockOptimistic)
For Each dr As DataRow In inTable.Rows
result.AddNew(System.Reflection.Missing.Value, System.Reflection.Missing.Value)
For columnIndex As Integer = 0 To inColumns.Count - 1
resultFields(columnIndex).Value = dr(columnIndex)
Next
Next
Return result
End Function
Shared Function TranslateType(ByVal columnType As Type) As ADODB.DataTypeEnum
Select Case columnType.UnderlyingSystemType.ToString()
Case "System.Boolean"
Return ADODB.DataTypeEnum.adBoolean
Case "System.Byte"
Return ADODB.DataTypeEnum.adUnsignedTinyInt
Case "System.Char"
Return ADODB.DataTypeEnum.adChar
Case "System.DateTime"
Return ADODB.DataTypeEnum.adDate
Case "System.Decimal"
Return ADODB.DataTypeEnum.adCurrency
Case "System.Double"
Return ADODB.DataTypeEnum.adDouble
Case "System.Int16"
Return ADODB.DataTypeEnum.adSmallInt
Case "System.Int32"
Return ADODB.DataTypeEnum.adInteger
Case "System.Int64"
Return ADODB.DataTypeEnum.adBigInt
Case "System.SByte"
Return ADODB.DataTypeEnum.adTinyInt
Case "System.Single"
Return ADODB.DataTypeEnum.adSingle
Case "System.UInt16"
Return ADODB.DataTypeEnum.adUnsignedSmallInt
Case "System.UInt32"
Return ADODB.DataTypeEnum.adUnsignedInt
Case "System.UInt64"
Return ADODB.DataTypeEnum.adUnsignedBigInt
End Select
Return ADODB.DataTypeEnum.adVarChar
End Function
Private Sub DtToExcelBtn_Click(sender As System.Object, e As System.EventArgs) Handles DtToExcelBtn.Click
Dim starttime = Now.ToString
Dim objExcel = CreateObject("Excel.Application")
Dim objWorkbook = objExcel.Workbooks.Add()
Dim objWorksheet = objWorkbook.Worksheets(1)
Dim i = 1
Dim rownumber = 1
objExcel.Visible = True
Do While (i < dt.Rows.Count)
Dim colNum As Integer = 0
Do While (colNum < dt.Columns.Count)
objWorksheet.Cells((i + rownumber), (colNum + 1)) = dt.Rows(i)(colNum).ToString
colNum = (colNum + 1)
Loop
i = (i + 1)
Loop
Dim endtime = Now.ToString
MsgBox(starttime & vbCrLf & endtime)
End Sub
End Class
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