I would like toI put two textboxes into an update panel so that they when either text changes, the emailtextbox is cleared(purple text below).  The code in purple is not happening.  The emailtextbox is what a popupextender and radiobuttonlist is applied to.  AJAX knows the two texboxes are updating since the radiobuttonlist is updated, but why doesn't the emailtextbox get cleared.  The code is in the same place.  
 

    Protected Sub lastTextBox_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles lastTextBox.TextChanged
        emailTextBox.Text = ""
        Dim UP1 As UpdatePanel = CType(FindControl("updatepanel1"), UpdatePanel)
        Dim RB1 As RadioButtonList = CType(UP1.FindControl("radiobuttonlist1"), RadioButtonList)
        RB1.DataBind()
    End Sub

    Protected Sub firstTextBox_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles firstTextBox.TextChanged
        emailTextBox.Text = ""
        Dim UP1 As UpdatePanel = CType(FindControl("updatepanel1"), UpdatePanel)
        Dim RB1 As RadioButtonList = CType(UP1.FindControl("radiobuttonlist1"), RadioButtonList)
        RB1.DataBind()
    End Sub

The TextChanged event of the TextBox server control is only fired after a postback.  It then looks to see if the text property of the textbox has changed.  It is not something that happens in response to the user just typing in the textbox.  You can give the textbox an onkeyup attribute (<asp:TextBox ID="TextBox1" runat="server" onkeyup="clearEmail();" />).

<script language="javascript" type="text/javascript">   
    function clearEmail() {
        document.getElementById('emailTextBox').value = '';
    }
</script>

I decided to use the onChange event for the textbox to run the javascript.  The key was learning that the ontextchange event won't happen.  Is there a way for the same javascript to tell the radiobuttonlist to bind from the lastTextbox.  The radiobuttonlist datasource uses the lastTextbox value as a parameter.  Now that the lastTextbox is empty, I need for the readiobuttonlist to refresh its data. 

No, javascript can only manipulate those document objects on the page.  I has not control over server interactions.  However, what you can do is cause a postback, during which the radio controls will rebind.  The javascript should be something along these lines: 

<script language="javascript" type="text/javascript">
    function clearEmail() {
        document.getElementById('TextBox2').value = '';
        __doPostBack('TextBox1', '');
    }
</script>

That does it. Thanks.  Just to be clear, the _doPostBack... causes the entire page to postback, right?

Yes, but you could easily set this up as a partial-postback scenario: 

• Place the radio lists in an updatepanel(s).
• Set the event target of the __doPostBack() call as an asynch target of the updatepanel(s).

For further details, read http://encosia.com/2007/07/13/easily-refresh-an-updatepanel-using-javascript/.

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