Optimal way to Read an Excel file (.xls/.xlsx)

Question

I know that there are different ways to read an Excel file:

• Iterop
• Oledb
• Open Xml SDK

C

Answer 1

Read from excel, modify and write back

 /// 

/// /Reads an excel file and converts it into dataset with each sheet as each table of the dataset
/// 
/// 
/// If set to true the first row will be considered as headers
/// 
public DataSet Import(string filename, bool headers = true)
{
    var _xl = new Excel.Application();
    var wb = _xl.Workbooks.Open(filename);
    var sheets = wb.Sheets;
    DataSet dataSet = null;
    if (sheets != null && sheets.Count != 0)
    {
        dataSet = new DataSet();
        foreach (var item in sheets)
        {
            var sheet = (Excel.Worksheet)item;
            DataTable dt = null;
            if (sheet != null)
            {
                dt = new DataTable();
                var ColumnCount = ((Excel.Range)sheet.UsedRange.Rows[1, Type.Missing]).Columns.Count;
                var rowCount = ((Excel.Range)sheet.UsedRange.Columns[1, Type.Missing]).Rows.Count;

                for (int j = 0; j < ColumnCount; j++)
                {
                    var cell = (Excel.Range)sheet.Cells[1, j + 1];
                    var column = new DataColumn(headers ? cell.Value : string.Empty);
                    dt.Columns.Add(column);
                }

                for (int i = 0; i < rowCount; i++)
                {
                    var r = dt.NewRow();
                    for (int j = 0; j < ColumnCount; j++)
                    {
                        var cell = (Excel.Range)sheet.Cells[i + 1 + (headers ? 1 : 0), j + 1];
                        r[j] = cell.Value;
                    }
                    dt.Rows.Add(r);
                }

            }
            dataSet.Tables.Add(dt);
        }
    }
    _xl.Quit();
    return dataSet;
}



 public string Export(DataTable dt, bool headers = false)
    {
        var wb = _xl.Workbooks.Add();
        var sheet = (Excel.Worksheet)wb.ActiveSheet;
        //process columns
        for (int i = 0; i < dt.Columns.Count; i++)
        {
            var col = dt.Columns[i];
            //added columns to the top of sheet
            var currentCell = (Excel.Range)sheet.Cells[1, i + 1];
            currentCell.Value = col.ToString();
            currentCell.Font.Bold = true;
            //process rows
            for (int j = 0; j < dt.Rows.Count; j++)
            {
                var row = dt.Rows[j];
                //added rows to sheet
                var cell = (Excel.Range)sheet.Cells[j + 1 + 1, i + 1];
                cell.Value = row[i];
            }
            currentCell.EntireColumn.AutoFit();
        }
        var fileName="{somepath/somefile.xlsx}";
        wb.SaveCopyAs(fileName);
        _xl.Quit();
        return fileName;
    }