How do I auto size columns through the Excel interop objects?

Below is the code I'm using to load the data into an Excel worksheet, but I'm look to auto size the column after the data is loaded. Does anyone know the best way to auto size the columns?

using Microsoft.Office.Interop;

public class ExportReport
{
	public void Export()
	{
		Excel.Application excelApp = new Microsoft.Office.Interop.Excel.Application();
		Excel.Workbook wb;
		Excel.Worksheet ws;
		Excel.Range aRange;
		object m = Type.Missing;
		string[,] data;
		string errorMessage = string.Empty;
		try
		{
			if (excelApp == null)
				throw new Exception("EXCEL could not be started.");

			// Create the workbook and worksheet.
			wb = excelApp.Workbooks.Add(Office.Excel.XlWBATemplate.xlWBATWorksheet);
			ws = (Office.Excel.Worksheet)wb.Worksheets[1];

			if (ws == null)
				throw new Exception("Could not create worksheet.");

			// Set the range to fill.
			aRange = ws.get_Range("A1", "E100");

			if (aRange == null)
				throw new Exception("Could not get a range.");

			// Load the column headers.
			data = new string[100, 5];
			data[0, 0] = "Column 1";
			data[0, 1] = "Column 2";
			data[0, 2] = "Column 3";
			data[0, 3] = "Column 4";
			data[0, 4] = "Column 5";

			// Load the data.
			for (int row = 1; row < 100; row++)
			{
				for (int col = 0; col < 5; col++)
				{
					data[row, col] = "STUFF";
				}
			}

			// Save all data to the worksheet.
			aRange.set_Value(m, data);
			// Atuo size columns
			// TODO: Add Code to auto size columns.

			// Save the file.
			wb.SaveAs("C:\Test.xls", Office.Excel.XlFileFormat.xlExcel8, m, m, m, m, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlNoChange, m, m, m, m, m);
			// Close the file.
			wb.Close(false, false, m);
		}
		catch (Exception) { }
		finally
		{
			// Close the connection.
			cmd.Close();
			// Close Excel.
			excelApp.Quit();
		}
	}
}

Add this at your TODO point:

aRange.Columns.AutoFit();

This might be too late but if you add

 worksheet.Columns.AutoFit();

or

 worksheet.Rows.AutoFit();

it also works.

Also there is

aRange.EntireColumn.AutoFit();

See https://stackoverflow.com/questions/3058062/see-the-difference-between-range-columns-and-range-entirecolumn.

This method opens already created excel file, Autofit all columns of all sheets based on 3rd Row. As you can see Range is selected From "A3 to K3" in excel.

 public static void AutoFitExcelSheets()
    {
        Microsoft.Office.Interop.Excel.Application _excel = null;
        Microsoft.Office.Interop.Excel.Workbook excelWorkbook = null;
        try
        {
            string ExcelPath = ApplicationData.PATH_EXCEL_FILE;
            _excel = new Microsoft.Office.Interop.Excel.Application();
            _excel.Visible = false;
            object readOnly = false;
            object isVisible = true;
            object missing = System.Reflection.Missing.Value;

            excelWorkbook = _excel.Workbooks.Open(ExcelPath,
                   0, false, 5, "", "", false, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "",
                   true, false, 0, true, false, false);
            Microsoft.Office.Interop.Excel.Sheets excelSheets = excelWorkbook.Worksheets;
            foreach (Microsoft.Office.Interop.Excel.Worksheet currentSheet in excelSheets)
            {
                string Name = currentSheet.Name;
                Microsoft.Office.Interop.Excel.Worksheet excelWorksheet = (Microsoft.Office.Interop.Excel.Worksheet)excelSheets.get_Item(Name);
                Microsoft.Office.Interop.Excel.Range excelCells =
(Microsoft.Office.Interop.Excel.Range)excelWorksheet.get_Range("A3", "K3");
                excelCells.Columns.AutoFit();
            }
        }
        catch (Exception ex)
        {
            ProjectLog.AddError("EXCEL ERROR: Can not AutoFit: " + ex.Message);
        }
        finally
        {
            excelWorkbook.Close(true, Type.Missing, Type.Missing);
            GC.Collect();
            GC.WaitForPendingFinalizers();
            releaseObject(excelWorkbook);
            releaseObject(_excel);
        }
    }

Have a look at this article, it's not an exact match to your problem, but suits it:

• Craig Murphy - Excel – wordwrap row autosize issue