I want to create an excel having extension xlsx/xls.

<asp:Button ID="btnGetEmptyTemplate" runat="server" 
              Text="Download Empty template for Import" CssClass="btn btn-default" 
              onclick="btnGetEmptyTemplate_Click"/>

 protected void btnGetEmptyTemplate_Click(object sender, EventArgs e)
        {
            GetTemplate();
        }

private void GetTemplate()
        {
            try
            {   //create new xls file
                string file = "C:\\newdoc.xls";
                Workbook workbook = new Workbook();
                Worksheet worksheet = new Worksheet("First Sheet");
                Workbook wb = excel.Workbooks.Add(System.Reflection.Missing.Value);
                
               
            }
            catch (Exception ex)
            {

                throw ex;
            }
        }