You have only have one radio button
per container or
group selected at any one time.
To have more than one radiobutton selected then you must group the radio buttons - e.g. put the radiobuttons for one option into a Panel control, and for another option into another Panel control.
You can also utilise the
GroupName
property for the RadioButtons - this way even if they are in the same container they will still work as a group e.g.
<asp:Panel ID="Panel1" runat="server">
<asp:RadioButton ID="RadioButton1" runat="server" GroupName="Group1" />
<asp:RadioButton ID="RadioButton2" runat="server" GroupName="Group1" />
<asp:RadioButton ID="RadioButton3" runat="server" GroupName="Group2" />
<asp:RadioButton ID="RadioButton4" runat="server" GroupName="Group2" />
</asp:Panel>
If however, you want to have multiple selections within the group then use CheckBoxes or a CheckBoxList