Listbox control does not pass the selected value when clicked

flashmanTom · July 6th, 2011, 12:11 PM

Hi,

I am trying to work the delete role example in chapter 16. Just as an exercise, I'm trying to get the role clicked in the listbox deleted from the list. However, the list box doesn't return the selected value.

Here is my code:

<code>
<%@PageLanguage="C#" %>
<!DOCTYPEhtmlPUBLIC"-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<scriptrunat="server">
protected void Page_Load(object sender, EventArgs e)
{
Page.SetFocus(TextBox1);
ListBoxDataBind();
}

protected void Button1_Click(object sender, EventArgs e)
{
Roles.CreateRole(TextBox1.Text.ToString());
ListBoxDataBind();
TextBox1.Text = "";
}
protected void ListBoxDataBind()
{
ListBox1.DataSource = Roles.GetAllRoles();
ListBox1.DataBind();
}
protected void DeleteButton_Click(object sender, EventArgs e)
{
if (ListBox1.SelectedValue != "")
{
Roles.DeleteRole(ListBox1.SelectedValue);
ListBoxDataBind();
}
}
</script>
<htmlxmlns="http://www.w3.org/1999/xhtml">
<headrunat="server">
<title>Role Manager</title>
</head>
<body>
<formid="form1"runat="server">
<h1>Role Manager</h1>
<b>Add Role:</b><br/>
<asp:TextBoxID="TextBox1"runat="server"></asp:TextBox>
<p><asp:ButtonID="Button1"runat="server"Text="Add Role to Application"OnClick="Button1_Click"/></p>
<b>Roles Defined:</b><br/>
<asp:ListBoxID="ListBox1"runat="server"></asp:ListBox>
<p><asp:ButtonID="DeleteButton"runat="server"Text="Delete Role"OnClick="DeleteButton_Click"/></p>
</form>
</body>
</html>
</code>

Any help will be appreciated.

flashmanTom

Imar · July 6th, 2011, 02:26 PM

Hi there,

It's because you're rebinding the list on each post back. Try this instead:

Code:

 
protected void Page_Load(object sender, EventArgs e)
{
  Page.SetFocus(TextBox1);
  if (!Page.IsPostBack)
  {   
    ListBoxDataBind();
  }
}

Hope this helps,

Imar

flashmanTom · July 7th, 2011, 11:55 AM

Hi Imar,

Thanks for the info.

Tom

NdAsit1441 · May 21st, 2012, 06:00 AM

I have bind the list box control in page post back event.
when application is running in ipad, the control get changed from listbox to dropdown shape and on button click it does not get the selected value.
but the same thing is working on a different page