ASP.Net DropdownList control can be placed inside ItemTemplate of TemplateField column of GridView control. To bind the data with nested Dropdownlist control you can use C# foreach loop over each Row Item of GridView control and FindControl method to find the DropdownList control and get its reference in the C# code.
C# Methods Used
1. foreach loop
2. FindControl method to find and bind the nested Dropdownlist control