Checkbox values are not updating by row wise

In my gridview i having 7 checkboxes,while updating the checkbox which i have checked last it is updated in the database other values are been cleared..for eg we have day_id as mon is 1,tues as 2 ,wen as 3,thurs as 4,fri as 5,sat as 6,sun as 7(if i checked mon and tues checkboxes means,only tues check box values are been updated in database mon value is updated as null.there is no seprate column for days only the dayid i will pass....

this is my coding....

if (chkMonday.Checked == true)
    {
        int MonStatus;
        MonStatus = 1;
        SwipeCardLeaveFacade.UpdateCalendarDay(Calenderid, MonStatus, UserContext, RequestContext);
    }
    if (chkTuesday.Checked == true)
    {
        int TueStatus;
        TueStatus = 2;
        SwipeCardLeaveFacade.UpdateCalendarDay(Calenderid, TueStatus, UserContext, RequestContext);
    }
    if (chkWednesday.Checked == true)
    {
        int WedStatus;
        WedStatus = 3;
        SwipeCardLeaveFacade.UpdateCalendarDay(Calenderid, WedStatus, UserContext, RequestContext);
    }
    if (chkThrusday.Checked == true)
    {
        int ThuStatus;
        ThuStatus = 4;
        SwipeCardLeaveFacade.Updat开发者_如何学JAVAeCalendarDay(Calenderid, ThuStatus, UserContext, RequestContext);
    }
    if (chkFriday.Checked == true)
    {
        int FriStatus;
        FriStatus = 5;
        SwipeCardLeaveFacade.UpdateCalendarDay(Calenderid, FriStatus, UserContext, RequestContext);
    }
    if (chkSaturday.Checked == true)
    {
        int SatStatus;
        SatStatus = 6;
        SwipeCardLeaveFacade.UpdateCalendarDay(Calenderid, SatStatus, UserContext, RequestContext);
    }
    if (chkSunday.Checked == true)
    {
        int SunStatus;
        SunStatus = 7;
        SwipeCardLeaveFacade.UpdateCalendarDay(Calenderid, SunStatus, UserContext, RequestContext);
    }

This is my stored procedure....

Create  Procedure Sp_Update_LMS_CalendarDay  
(    

   @CalendarDay_CalendarID int,    
   @CalendarDay_DayID  int    
)    
as  
update  LMS_CalendarDay  
set  
CalendarDay_CalendarID=@CalendarDay_CalendarID,  
CalendarDay_DayID=@CalendarDay_DayID  
where   
CalendarDay_CalendarID=@CalendarDay_CalendarID

My table columns is CalendarDay_CalendarID CalendarDay_DayID here CalendarDay_DayID will goes as 1,2,3,4,5,6,7

Correct me if I'm wrong.

Your Update Function for all days (Mon to Sun) is using the same CalendarId. For e.g. I checked Mon and Tues. Your Stored Procedure will be invoked twice using the same CalendarId, thus overwriting your last update action. Only Tues will be updated in the db.