The HTMLSelect.Name is always the same as its ID/UniqueID properties. The documentation states:

Use the Name property to determine the unique identifier name for an HtmlSelect control. In this implementation, the get accessor returns the value of the Control.UniqueID property. However, the set accessor does not assign a value to this property.

The set accessor does not assign a value to this property because the Name property must have the same value as the Control.UniqueID property for the HtmlSelect control to work properly.

Thus, you can’t output an HTML <select> element that has different values for the “name” property and “id” attributes… unless you re-implement the code to do so yourself.

This isn’t the case for most other controls in the System.Web.UI.HtmlControls namespace. There’s no stated reason why the restriction is so necessary either. You have to really wonder WTF is going on over at Microsoft for a team to code in a seemingly arbitrary restriction and document it but not fix the problem in the first place.