<td> style to force the cell as number: mso-number-format:General;
Code Behind(cs) file
public PartialViewResult ExcelFile()
{
StringBuilder table = new StringBuilder();
table.AppendLine("<table>");
table.AppendLine("<thead>");
table.AppendLine("<tr>");
table.AppendLine("<th>Date</th>");
table.AppendLine("<th>Store</th>");
table.AppendLine("</tr>");
table.AppendLine("</thead>");
table.AppendLine("<tbody>");
table.AppendLine("<tr>");
table.Append("<td>10/27/2016</td>");
table.Append("<td style='mso-number-format:\"\\@\"'>0001</td>");
table.AppendLine("</tr>");
table.AppendLine("<tr>");
table.Append("<td>10/27/2016</td>");
table.Append("<td style='mso-number-format:\"\\@\"'>0002</td>");
table.AppendLine("</tr>");
table.AppendLine("</tbody>");
table.AppendLine("</table>");
Response.ContentType = "application/force-download";
Response.AddHeader("content-disposition", "attachment; filename=ExcelFile_" + DateTime.Now.ToString("yyyyMMddhhmmss") + ".xls");
Response.Write("<html xmlns:x=\"urn:schemas-microsoft-com:office:excel\">");
Response.Write("<head>");
Response.Write("<META http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\">");
Response.Write("<!--[if gte mso 9]><xml>");
Response.Write("<x:ExcelWorkbook>");
Response.Write("<x:ExcelWorksheets>");
Response.Write("<x:ExcelWorksheet>");
Response.Write("<x:Name>ExcelFile</x:Name>");
Response.Write("<x:WorksheetOptions>");
Response.Write("<x:Print>");
Response.Write("<x:ValidPrinterInfo/>");
Response.Write("</x:Print>");
Response.Write("</x:WorksheetOptions>");
Response.Write("</x:ExcelWorksheet>");
Response.Write("</x:ExcelWorksheets>");
Response.Write("</x:ExcelWorkbook>");
Response.Write("</xml>");
Response.Write("<![endif]--> ");
Response.Write("</head>");
Response.Write(table.ToString());
Response.Flush();
return PartialView();
}
