<!-- Countries for selection -->
<asp:DataGrid id="countriesGrid" runat="server"
         DataKeyField="ID" AutoGenerateColumns="False">
    <Columns>
        <asp:TemplateColumn>
            <ItemTemplate>
                <!--
                Draw attention at this control.
                We would like to use radio-buttons to
                select single country from the list.
                -->
                <asp:RadioButton id="selectRadioButton"
                    runat="server" GroupName="country" />
            </ItemTemplate>
        </asp:TemplateColumn>
        <asp:BoundColumn DataField="Country" HeaderText="Country"
                                  HeaderStyle-Font-Bold="True" />
        <asp:BoundColumn DataField="Capital" HeaderText="Capital"
                                  HeaderStyle-Font-Bold="True" />
    </Columns>
</asp:DataGrid>

Now, bind to the DataGrid some data and run your ASP.NET application. Try to click at the radio buttons in the Countries list. You can select one country!... and another one... and another... Hmm-m! Didn't we really want to get this effect?

Where is a mistake? We have specified GroupName for the RadioButtons to treat them as from the single group, haven't we? Look at the piece of HTML code that has been generated from our web form. You will see something like this:

<!-- Countries for selection -->
<table cellspacing="0" rules="all" border="1" id="countriesGrid"
                              style="border-collapse:collapse;">
    <tr>
        <td> </td>
        <td style="font-weight:bold;">Country</td>
        <td style="font-weight:bold;">Capital</td>
    </tr>
    <tr>
        <td><input id="countriesGrid__ctl2_selectRadioButton"
             type="radio" name="countriesGrid:_ctl2:country"
             value="selectRadioButton" /></td>
        <td>USA</td>
        <td>Washington</td>
    </tr>
    <tr>
        <td><input id="countriesGrid__ctl3_selectRadioButton"
             type="radio" name="countriesGrid:_ctl3:country"
             value="selectRadioButton" /></td>
        <td>Canada</td>
        <td>Ottawa</td>
    </tr>
    <!-- etc. -->

The 'name' attributes of the radio-buttons are different. Why? Here is the answer.

When rendering RadioButton control, ASP.NET uses concatenation of GroupName and UniqueID for the value of 'name' attribute. So, this attribute depends on the UniqueID of the control which depends on the owner's UniqueID etc. It is the standard solution of ASP.NET to avoid naming collisions.

As the value of the 'name' attribute of the <input type="radio" /> is used for identification of postback data of the radio-button group when the from is submitting, ASP.NET developers decided to isolate radio-button groups within the bounds of the single owner control (i.e., any two radio-buttons from the same group can not have different direct owners), otherwise it can occur that you will use two third party controls that both contain radio-button groups with the same GroupName - in this case, all radio-buttons will be treated as from the single group and that will bring undesirable behavior. 

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