DropDownList.SelectedValue returns UpperCase string.

I’ve noticed that DropDownList.SelectedValue returns Upper Case string, even if Items in ListItemCollection are shown in mixed case in debugger and in html.
I tried to confirm it using Reflector , but didn’t find particular code to call ToUpper.

Is it only my application or .Net framework(I am using 2.0) ?

Anyway, it is a good practice to call ToUpper() if you want to compare  DropDownList.SelectedValue with other strings.