WebForm1.aspx :-
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="video8_IsPostBackProperty.WebForm1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<style type="text/css">
.style1
{
width: 114px;
}
.style2
{
width: 114px;
height: 23px;
}
.style3
{
height: 23px;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<div>
<table style="width: 70%;">
<tr>
<td class="style1">
<asp:Label ID="Label1" runat="server" Text="First Name"></asp:Label>
</td>
<td>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</td>
</tr>
<tr>
<td class="style1">
<asp:Label ID="Label2" runat="server" Text="Last Name"></asp:Label>
</td>
<td>
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
</td>
</tr>
<tr>
<td class="style2">
<asp:Label ID="Label3" runat="server" Text="City"></asp:Label>
</td>
<td class="style3">
<asp:DropDownList ID="DropDownList1" runat="server">
</asp:DropDownList>
</td>
</tr>
<tr>
<td class="style1" colspan="1" rowspan="1">
</td>
<td colspan="1" rowspan="1">
<asp:Button ID="Button1" runat="server"
Text="Register Employee" />
</td>
</tr>
</table>
<br />
</div>
</form>
</body>
</html>
WebForm1.aspx.cs :-
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace video8_IsPostBackProperty
{
public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
LoadCityDropDownList();
//Or disable the view state of the drop downlist as Enable View State
//Or DropDownList1.Items.Clear();LoadCityDropDownList();
}
public void LoadCityDropDownList()
{
ListItem li1 = new ListItem("London");
DropDownList1.Items.Add(li1);
ListItem li2 = new ListItem("Sydni");
DropDownList1.Items.Add(li2);
ListItem li3 = new ListItem("paris");
DropDownList1.Items.Add(li3);
}
}
}
Every time you click the button dropdownlist items will duplicated. we can use the IsPostBack property to solve this problem.
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