title: How to Check RadioButtonList when Option Selected is Changed?
body: <p>I have a .NET/ASP.NET based form that uses a RadioButtonList in which by default none of the options are selected:</p>
  
  <pre><code>&lt;%@ Control Language="C#" AutoEventWireup="true" CodeFile="Rb.ascx.cs" Inherits="Rb" %&gt;
  &lt;table&gt;&lt;tr&gt;&lt;td align="left"&gt;
  &lt;asp:RadioButtonList ID="radioButtonList" runat="server"&gt;
  &lt;/asp:RadioButtonList&gt;
  &lt;/td&gt;&lt;td valign="top"&gt;
  &lt;asp:RequiredFieldValidator ID="radioButtonListValidator" runat="server" ControlToValidate="radioButtonList" ErrorMessage=": Please select an option." Text="*" ValidationGroup="validate"&gt;
  &lt;/asp:RequiredFieldValidator&gt;
  &lt;/td&gt;&lt;/tr&gt;
  &lt;/table&gt;
  </code></pre>
  
  <p>For one of the options in the list, <strong>as soon as it's selected</strong> I would like to generate a warning message box (rather than using some sort of description label or validation error message). So far as I can tell, there's no event handler for something like _SelectChanged. I was wondering how to implement such a feature to get something like this (below is semi-psuedocode because I'm not sure how to code what I want given the seemingly lack of an event handler for what I want):</p>
  
  <pre><code>public override void radioButtonList_SelectionChanged(Object sender, EventArgs e)
  {
      if(radioButtonList.SelectedItem == "Option 2") //Where 'Option 2' is displayed on the actual form next to the radio button
      {
          Messagebox.Show("Warning: Selecting this option may release deadly neurotoxins");
      }
  }
  </code></pre>