Check your item names: does "drp1" exist?
If it does, then split your lines, and check each part in turn:
Dim obj = e.Item.FindControl("drp1")
Is
obj
equal to
Nothing
? If it is double check the name!
If not, then
Dim ddlTenure As DropDownList = TryCast(obj, DropDownList)
Is
ddlTenure
equal to
Nothing
? If it is, then you need to check the actual type of the dropdown and correct that.
Finally, check
ddlTenure.SelectedItem
against
Nothing
- if there is nothing selected, that will be your problem.