PostImport.cs

public ActionResult OnPostImport()
{
    IFormFile file = Request.Form.Files[0];
    string folderName = "Upload";
    string webRootPath = _hostingEnvironment.WebRootPath;
    string newPath = Path.Combine(webRootPath, folderName);
    StringBuilder sb = new StringBuilder();
    if (!Directory.Exists(newPath))
    {
        Directory.CreateDirectory(newPath);
    }
    if (file.Length > 0)
    {
        string sFileExtension = Path.GetExtension(file.FileName).ToLower();
        ISheet sheet;
        string fullPath = Path.Combine(newPath, file.FileName);
        using (var stream = new FileStream(fullPath, FileMode.Create))
        {
            file.CopyTo(stream);
            stream.Position = 0;
            if (sFileExtension == ".xls")
            {
                HSSFWorkbook hssfwb = new HSSFWorkbook(stream); //This will read the Excel 97-2000 formats  
                sheet = hssfwb.GetSheetAt(0); //get first sheet from workbook  
            }
            else
            {
                XSSFWorkbook hssfwb = new XSSFWorkbook(stream); //This will read 2007 Excel format  
                sheet = hssfwb.GetSheetAt(0); //get first sheet from workbook   
            }
            IRow headerRow = sheet.GetRow(0); //Get Header Row
            int cellCount = headerRow.LastCellNum;
            sb.Append("<table class='table'><tr>");
            for (int j = 0; j < cellCount; j++)
            {
                NPOI.SS.UserModel.ICell cell = headerRow.GetCell(j);
                if (cell == null || string.IsNullOrWhiteSpace(cell.ToString())) continue;
                sb.Append("<th>" + cell.ToString() + "</th>");
            }
            sb.Append("</tr>");
            sb.AppendLine("<tr>");
            for (int i = (sheet.FirstRowNum + 1); i <= sheet.LastRowNum; i++) //Read Excel File
            {
                IRow row = sheet.GetRow(i);
                if (row == null) continue;
                if (row.Cells.All(d => d.CellType == CellType.Blank)) continue;
                for (int j = row.FirstCellNum; j < cellCount; j++)
                {
                    if (row.GetCell(j) != null)
                        sb.Append("<td>" + row.GetCell(j).ToString() + "</td>");
                }
                sb.AppendLine("</tr>");
            }
            sb.Append("</table>");
        }
    }
    return this.Content(sb.ToString());
}