I don't know asp.net but normally you would add a value to your radio buttons.
<input runat="server" type="radio" name="radio" id="radio0" value="0"> Radio Button 0
<br>
<input runat="server" type="radio" name="radio" id="radio1" value="1"> Radio Button 1
And submitting the form would return the selected radio button value for the name attribute parameter (in this case you named it radio
).