private void button1_Click(object sender, EventArgs e)
{
    string excelFinalPath = @"C:\Users\pulsani\Desktop\MS_Excel\data.xlsx";
    Microsoft.Office.Interop.Excel.Application application = new Microsoft.Office.Interop.Excel.Application();
    Workbook workBook = application.Workbooks.Open(excelFinalPath);
    /////////////////////////////////////////////////////////////////
    DataSet dataSet = new DataSet();

    for (int i = 1; i <= workBook.Sheets.Count; i++)
    {
        Worksheet worksheet = workBook.Worksheets[i];

        Range excelCell = worksheet.UsedRange;
        Object[,] sheetValues = (Object[,])excelCell.Value;
        int noOfRows = sheetValues.GetLength(0); // first dimention size
        int noOfColumns = sheetValues.GetLength(1);//second dimention size

        //add column names to datatable
        System.Data.DataTable dataTable = new System.Data.DataTable();
        for (int j = 1; j <= noOfColumns; j++)
        {
            dataTable.Columns.Add(new DataColumn(((Range)worksheet.Cells[1, j]).Value));
        }

        //as first column has header, start at second row
        for (int k = 2; k <= noOfRows; k++)
        {
            DataRow dataRow = dataTable.NewRow();
            for (int l = 1; l <= noOfColumns; l++)
            {
                dataRow[l - 1] = ((Range)worksheet.Cells[k, l]).Value;
            }
            dataTable.Rows.Add(dataRow);
        }
        dataSet.Tables.Add(dataTable);
    }
    /////////////////////////////////////////////////////////////////
    workBook.Close(false, excelFinalPath, null);
    Marshal.ReleaseComObject(workBook);
}