Input String Was Not In A Correct Format error will coming in following code check this correct code.

string mac_rate_eff_date = DateTime.Now.ToString("yy-M-dd");
       string FromDate = "";
       if (tabname == "ItemOfMachinery")
       {
           if (dbwork == "Insert")
           {
               imacc_id = int.Parse(drpcategoryofmachinery.SelectedValue);
               mac_code = txtcode.Text;
               ma_short_desc = txtshort.Text;
               mac_long_desc = txtDescription.Text;
               mac_unit = int.Parse(drpUnit.SelectedItem.Value);
               mac_rate = double.Parse(drpcategoryofmachinery.SelectedValue);
               FromDate = txteffdate.Text;

               string[] datesplit = FromDate.Split('-');
               mac_rate_eff_date = datesplit[2] + "-" + datesplit[1] + "-" + datesplit[0];

               if (datesplit[0].Length == 4)
               {
                   mac_rate_eff_date = datesplit[0] + "-" + datesplit[1] + "-" + datesplit[2];
               }
           }
           else
           {
               mac_id = int.Parse(hdnmac_id.Value);
               mac_rate_id = int.Parse(hdnmac_rate_id.Value);
               imacc_id = int.Parse(drpcategoryofmachinery.SelectedValue);
               ma_short_desc = hdnshortdesc.Value;
               mac_long_desc = hdnlongdesc.Value;
               mac_unit = 0;
               mac_rate =double.Parse(hdnrate.Value);
               FromDate = hdnmac_effdate.Value;
               string[] datesplit = FromDate.Split('-');
               mac_rate_eff_date = datesplit[2] + "-" + datesplit[1] + "-" + datesplit[0];

               //if(datesplit[0].Length==4)
               //{
               //    mac_rate_eff_date = datesplit[0] + "-" + datesplit[1] + "-" + datesplit[2];
               //}

           }
           if (tabname == "ItemOfMachinery")
           {
               if (dbwork == "delete")
               {
                   mac_id = Convert.ToInt32(hdnmac_id.Value);
                   mac_rate_id = int.Parse(hdnmac_rate_id.Value);
               }
               else
               {
                   //imc_id = int.Parse(hdnworkid.Value);
                   //icode = hdncategorycode.Value;
                   //icatname = hdncategoryname.Value;
               }
           }