Please help:SelectedValue which is invalid

[frankie lo]

Hi All,

After add dropdownlist box into EditItemTemplate, I have gotten below error.
However, when i removed the databinding for selectedvalue of dropdownlist,
then error disappear but its field can't update. Do you have any suggestion
or idea to solve it? What can I do? I am using .Net2.0 & Visual Web
Developer 2005 Express.
'ddlClass' has a SelectedValue which is invalid because it does not exist in
the list of items.
Parameter name: value
Frankie.