foreach (GridViewRow row in GridViewDemo.Rows)
        {
            if (row.RowType == DataControlRowType.DataRow)
            {
                foreach(Control obj in row.Controls) 
                {
                    if (obj.GetType().BaseType.Name.ToUpper().Contains("RADIOBUTTON"))
                    { 
                    }
                }
            }
        }

 foreach (GridViewRow row in GridViewDemo.Rows)
        {
            if (row.RowType == DataControlRowType.DataRow)
            {
                RadioButton rb = row.FindControl("控件名称1");
                RadioButton rb = row.FindControl("控件名称2");
                RadioButton rb = row.FindControl("控件名称3");
                //得到三个单选按钮后就可以判断了
                //判断代码略...
            }
        }

------解决方案--------------------
按照lz的意思作了一个，看看是不是这样，我试了可以显示出被选按钮的ID
HTML code

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False">
        <Columns>
                <asp:TemplateField HeaderText="Select" ShowHeader="False">
                    <ItemTemplate>
                        <asp:RadioButton ID="RadioButton1" runat="server" Text="RadioButton1" GroupName="RadioGroup" />
                        <asp:RadioButton ID="RadioButton2" runat="server" Text="RadioButton2" GroupName="RadioGroup" />
                        <asp:RadioButton ID="RadioButton3" runat="server" Text="RadioButton3" GroupName="RadioGroup" />
                    </ItemTemplate>
                </asp:TemplateField>   
                <asp:BoundField DataField="insertTime" HeaderText="Time" />                             
            </Columns> 
        </asp:GridView>
        <br />
        <asp:Button ID="Button2" runat="server" Text="Button" OnClick="Button2_Click" />