Hello,

I have a VBA macro which fills a sheet with 65536 random integers, it
takes just over a minute to run on my laptop, a T5470 1.60 Dual Core
with 3.5GB Ram, running Vista, Excel 2007 and Visual Studio 2005. I
figured it might run faster in C#, in fact it runs 4 times slower and
then when you open the Spreadsheet, it complains about being in a
'different format than that specified in the file extension.... Verify
that the file is not corrupted..' - taking a long time to load,
perhaps another minute or two. Even given that the VBA is run from
within Excel, the C# version does seem extremely slow.

Is there anything fundamentally wrong with the C#?
Any tips on speeding it up?
Any way of making the format it is written to be 'straight xls',
rather than 'a different format.
A complete listing of the VBA sn the C# is given below.

Thanks for all constructive help given.
Hal
'------------ this VBA takes 1m 10s -------------------------
Option Explicit

Sub main()
Dim t1 As Date, t2 As Date
t1 = Time

Application.ScreenUpdating = False
Debug.Print "Start time: "; t1

Const mr = 2 ^ 16, mc = 2 ^ 8, L = 10 ^ 8, U = 9 * 10 ^ 8
Dim r As Long, c As Long
ReDim a(1 To mr, 1 To mc) As Long

For r = 1 To mr
For c = 1 To mc
a(r, c) = Int(U * Rnd + L)
Next c
Next r
Range(Cells(1, 1), Cells(mr, mc)) = a

Application.ScreenUpdating = True
t2 = Time
Debug.Print " End time: "; t2
Debug.Print "Time taken: "; Format(t2 - t1, "HH:MM:SS")
MsgBox "Time taken: " & Format(t2 - t1, "HH:MM:SS")
End Sub
'----------------------- end of VBA --------------------------
//------------- this C# takes over 4x as long ----------------
// Stage 1 took: 00:00:16.0970140
// Stage 2 took: 00:01:45.4888199
// Stage 3 took: 00:03:00.2385236
// Stage 4 took: 00:00:00.8334127
//
using System;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics; // timing
using System.Reflection;
using System.Runtime.InteropServices;
using Excel = Microsoft.Office.Interop.Excel;

namespace test4
{
class Program
{
static void Main(string[] args)
{
Stopwatch st = new Stopwatch();
// ----------------- Stage 1 ----------------------
st.Start();

// Excel object references.
Excel.Application m_objExcel = null;
Excel.Workbooks m_objBooks = null;
Excel._Workbook m_objBook = null;
Excel.Sheets m_objSheets = null;
Excel._Worksheet m_objSheet = null;
Excel.Range m_objRange = null;

// Frequenty-used variable for optional arguments.
object m = System.Reflection.Missing.Value;

// Paths used by the sample code for accessing and storing
data.
object m_strSampleFolder = "C:\\ExcelData\\";

// Start a new workbook in Excel.
m_objExcel = new Excel.Application();
m_objBooks = (Excel.Workbooks)m_objExcel.Workbooks;
m_objBook = (Excel._Workbook)(m_objBooks.Add(m));
m_objSheets = (Excel.Sheets)m_objBook.Worksheets;
m_objSheet = (Excel._Worksheet)(m_objSheets.get_Item(1));

const int maxrows = 65536; //65536=2^16=1<<16
const int maxcols = 256; //256=2^8=1<<8

object[,] objData = new Object[maxrows, maxcols];
Random rdm = new Random((int)DateTime.Now.Ticks);
//double nOrderAmt;//, nTax;

for (int r = 0; r < maxrows; r++)
{
for (int c = 0; c < maxcols; c++)
{
objData[r,c] = rdm.Next(100000000, 999999999);
}
}
st.Stop();
Console.WriteLine("Stage 1 took: {0}",
st.Elapsed.ToString());
// ----------------- Stage 2 ----------------------
st.Reset();
st.Start();

m_objRange = m_objSheet.get_Range("A1", m);
m_objRange = m_objRange.get_Resize(maxrows, maxcols);
m_objRange.set_Value(m, objData);

st.Stop();
Console.WriteLine("Stage 2 took: {0}",
st.Elapsed.ToString());
// ----------------- Stage 3 ----------------------
st.Reset();
st.Start();

// Save the workbook and quit Excel.
DateTime date = DateTime.Now;
m_objBook.SaveAs(m_strSampleFolder + "BigSheet-" +
date.ToString("yyyyMMdd_HHmmss.fff") + ".xls",

m,m,m,m,m,Excel.XlSaveAsAccessMode.xlNoChange,m,m, m,m,m);
m_objBook.Close(false,m,m);
m_objExcel.Quit();

st.Stop();
Console.WriteLine("Stage 3 took: {0}",
st.Elapsed.ToString());
// ----------------- Stage 4 ----------------------
st.Reset();
st.Start();

//Clean-up
m_objRange = null;
m_objSheet = null;
m_objSheets = null;
m_objBooks = null;
m_objBook = null;
m_objExcel = null;
GC.Collect();

st.Stop();
Console.WriteLine("Stage 4 took: {0}",
st.Elapsed.ToString());
}
}
}