asked on

Can not get (Listbox.Selecteditem.Value)

Can not get (Listbox.Selecteditem.Value)
It gives error (Object reference not set to an instance of an object)

Here is aspx code

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_default" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Button ID="Button1" runat="server" Text="Button" />
<asp:ListBox ID="ListBox1" runat="server"></asp:ListBox>
</div>
</form>
</body>
</html>

Here is the code behind

Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
ListBox1.Items.Clear()
ListBox1.Items.Add(New ListItem("saljas", "123"))
End Sub
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim xxx As String
'(the error is on the following line "Object reference not set to an instance of an object.")
xxx = ListBox1.SelectedItem.Value
'( note that (ListBox1.items count) works fine)
End Sub
End Class

Help is appreciated

ASKER CERTIFIED SOLUTION

Obadiah Christopher

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Salah a a a Al Jasem

ASKER

do you mean

(if the page is posted back then do not add to list)
If Page.IsPostBack Then Exit Sub
ListBox1.Items.Add(New ListItem("salah", "123"))

Or

(if the page is posted back then add to list)
If Page.IsPostBack Then
ListBox1.Items.Add(New ListItem("salah", "123"))
End if

SOLUTION