See my code below.
<asp:CheckBoxList ID="chkinfoSource" runat="server">
<asp:ListItem Text="Newspaper Ad" Value="Newspaper" />
<asp:ListItem Text="Radio Ad" Value="Radio" />
<asp:ListItem Text="Train Ad" Value="Train" />
<asp:ListItem Text="Other" Value="Other" />
</asp:checkboxList>
If other, please specify: <asp:TextBox ID="txtOther" runat="server" />
I need to make the user must choose some thing from the above control and
if the user selects other I need Make the txtOther as reqfield validator.
...
Go to the complete details ...