UserControl values lost on PostBack

[paul.hester@gmail.com]

Hi all,

I have a very simple user control that contains 3 drop downs. Whenever
there's a postback the values of these drop downs are lost. I've tried
enabling viewstate everywhere without success. Could anyone shed any
light on what's going wrong?

Thanks,

Paul

Asx:

<%@ Control Language="C#" EnableViewState="true" AutoEventWireup="true"
CodeFile="DayMonthYear.ascx.cs" Inherits="Test.DayMonthYear" %>
<%@ Register TagPrefix="test" Namespace="Test" %>
<table cellpadding="1" cellspacing="0">
<tr>
<td><small>Day</small></td>
<td><small>Month</small></td>
<td><small>Year</small></td>
</tr>
<tr>
<td><asp:DropDownList ID="day" EnableViewState="true"
runat="server"></asp:DropDownList></td>
<td><asp:DropDownList ID="month" EnableViewState="true"
runat="server"></asp:DropDownList></td>
<td><asp:DropDownList ID="year" EnableViewState="true"
runat="server"></asp:DropDownList></td>
</tr>
</table>

Asx.Cs:

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

namespace Test
{
public partial class DayMonthYear : System.Web.UI.UserControl,
INamingContainer
{
private int _yearHigh = DateTime.Now.Year;
private int _yearLow = DateTime.Now.Year - 100;

protected void Page_PreRender(object sender, EventArgs e)
{
string[] months = new string[] { "January", "February", "March",
"April", "May", "June", "July", "August", "September", "October",
"November", "December" };

// add days
day.Items.Add(new ListItem(string.Empty, "0"));
for (int i = 1; i < 32; i++)
day.Items.Add(i.ToString());

// add months
month.Items.Add(new ListItem(string.Empty, "0"));
for (int i = 0; i < months.Length; i++)
month.Items.Add(new ListItem(months[i], (i + 1) + string.Empty));

// add years
year.Items.Add(new ListItem(string.Empty, "0"));
for (int i = YearLow; i <= YearHigh; i++)
year.Items.Add(i.ToString());
}

public int YearHigh
{
get { return _yearHigh; }
set { _yearHigh = value; }
}

public int YearLow
{
get { return _yearLow; }
set { _yearLow = value; }
}
}
}

[Riki]

[email]paul.hester@gmail.com[/email] wrote:

> Hi all,
>
> I have a very simple user control that contains 3 drop downs. Whenever
> there's a postback the values of these drop downs are lost. I've tried
> enabling viewstate everywhere without success. Could anyone shed any
> light on what's going wrong?
>
> Thanks,
>
> Paul
>
> Asx:
>
> <%@ Control Language="C#" EnableViewState="true"
> AutoEventWireup="true" CodeFile="DayMonthYear.ascx.cs"
> Inherits="Test.DayMonthYear" %> <%@ Register TagPrefix="test"
> Namespace="Test" %> <table cellpadding="1" cellspacing="0">
> <tr>
> <td><small>Day</small></td>
> <td><small>Month</small></td>
> <td><small>Year</small></td>
> </tr>
> <tr>
> <td><asp:DropDownList ID="day" EnableViewState="true"
> runat="server"></asp:DropDownList></td>
> <td><asp:DropDownList ID="month" EnableViewState="true"
> runat="server"></asp:DropDownList></td>
> <td><asp:DropDownList ID="year" EnableViewState="true"
> runat="server"></asp:DropDownList></td>
> </tr>
> </table>
>
> Asx.Cs:
>
> using System;
> using System.Data;
> using System.Configuration;
> using System.Collections;
> using System.Web;
> using System.Web.Security;
> using System.Web.UI;
> using System.Web.UI.WebControls;
> using System.Web.UI.WebControls.WebParts;
> using System.Web.UI.HtmlControls;
>
> namespace Test
> {
> public partial class DayMonthYear : System.Web.UI.UserControl,
> INamingContainer
> {
> private int _yearHigh = DateTime.Now.Year;
> private int _yearLow = DateTime.Now.Year - 100;
>
> protected void Page_PreRender(object sender, EventArgs e)
> {
> string[] months = new string[] { "January", "February", "March",
> "April", "May", "June", "July", "August", "September", "October",
> "November", "December" };
>
> // add days
> day.Items.Add(new ListItem(string.Empty, "0"));
> for (int i = 1; i < 32; i++)
> day.Items.Add(i.ToString());
>
> // add months
> month.Items.Add(new ListItem(string.Empty, "0"));
> for (int i = 0; i < months.Length; i++)
> month.Items.Add(new ListItem(months[i], (i + 1) + string.Empty));
>
> // add years
> year.Items.Add(new ListItem(string.Empty, "0"));
> for (int i = YearLow; i <= YearHigh; i++)
> year.Items.Add(i.ToString());
> }
>
> public int YearHigh
> {
> get { return _yearHigh; }
> set { _yearHigh = value; }
> }
>
> public int YearLow
> {
> get { return _yearLow; }
> set { _yearLow = value; }
> }
> }
> }

If I understand your code well, you will get 12 months the first time,
24 after the first postback etc.

If so, in Pre_Render, use an if(!Page.IsPostBack) block for adding the
items. In other words, don't add items on postback again.

--

Riki