Please help to implement Dropdown list in my project

Hi,

Use requiredFieldValidator for validating 0 index of dropdownlist control.

DropDownList1" InitialValue="0"
                                                                Display="Dynamic" ErrorMessage="Please select Mark as">Mark as is required.

I think you should want to Mark As Inactive if I'm wrong pls correct me. If it is you can write like in indexchanged
if(DropDownList1.SelectedIndex==0)
{
//Do Nothing
}
else if(Index==1)
{
//Do Mark As
}
else if(Index==2)
{
//Do unMark
}
else
{
//Select The Value.
}