Two way binding with custom expression? - asp.net

Question

I am using a gridview in my asp.net project to view and modify some records from the database. The database has two columns: start_date and end_date. When a new record is created these columns contains null, but they can be modified later using the gridview update command.
In gridview I have two template fields (having names start_date and end_date) in which I have placed two calendar controls. Upon clicking an update link of gridview it always returns an error because of the null value binding to the calendar. I have used this helper function to solve it:
protected DateTime ReplaceNull(Object param)
{
if (param.Equals(DBNull.Value))
{
return DateTime.Now;
}
else
{
return Convert.ToDateTime(param);
}
}
and used these two custom expressions in calendar control's SelectedDate:
ReplaceNull(Eval("start_date"))
ReplaceNull(Eval("end_date"))
The problem is that two-way data binding the calendars upon selecting a date does not update the database table. Are there any workarounds? Or alternatively, a better solution would be appreciated.

Answer 1

I don't know why you let them null when insert a new record , but many ways you can solve this problem i think .
one of them : in the RowDataBound event of the Gridview
protected void gv_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
if (e.Row.Cells[1] == null) //the index of the start_date
{
e.Row.Cells[1].Text = DateTime.Now.ToString(); // in your case you will make the selected date of the calender(through casting to calender) with the value you need.
}
}
}
Or: you can catch the exception , you meet in your Update button through
try and catch block.