How to calculate percentage in viewbag after hitting submit button?

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C#

Visual-Studio

MVC

I tried to calculate the percentage of total count in viewbag after i click on the submit button. but the program is displaying the value before the submit button is clicked.

i understand the error as it says that error is because the system tried to divide the number by zero. but i dont have any idea on how to make it correctly. hope you can help as i'm still new in this language

What I have tried:

in view:

<tr style="text-align:center">
                            <td>@ViewBag.datepick.Count</td>
                            <td>@ViewBag.pass.Count</td>
                            <td></td>
                        </tr>

in controller:

public ActionResult TesterPerformance(string name, DateTime? start, DateTime? end)
       {


           var selectdate = (from c in db.Information
                             join t in db.Testers
                             on c.TesterID equals t.TesterID
                             join i in db.Parameters
                             on c.Stag_status equals i.ParameterID
                             where  c.Time_start >= start && c.Time_start <= end
                             select new DetailBundle
                             {
                                 Time_start = c.Time_start,
                                 Time_fail = c.Time_fail,
                                 Time_pass = c.Time_pass,
                                 Param_desc = i.Param_desc,
                                 TesterName = t.TesterName,
                                 Service_tag = c.Service_tag

                             }).ToList();
           ViewBag.datepick = selectdate;
           var selectpass = (from c in db.Information
                             join t in db.Testers
                             on c.TesterID equals t.TesterID
                             join i in db.Parameters
                             on c.Stag_status equals i.ParameterID
                             where c.Time_start >= start && c.Time_start <= end &&  i.Param_desc=="pass"
                             select new DetailBundle
                             {
                                 Time_start = c.Time_start,
                                 Time_fail = c.Time_fail,
                                 Time_pass = c.Time_pass,
                                 Param_desc = i.Param_desc,
                                 TesterName = t.TesterName,
                                 Service_tag = c.Service_tag

                             }).ToList();
           ViewBag.pass = selectpass;

           ViewBag.Percentage = (ViewBag.pass.Count / ViewBag.datepick.Count) * 100;
           return View();
       }

the submit button is in the same view