Develop Reference

CheckBoxlist Updating a dropdowlist in UpdatePanel no longer PostBack

I need to Update a Dropdowlist according to the selected value(s) in a CheckBoxList avoiding the page to reload, I am using an UpdatePanel.
The dropdwonlist should always have an AutoPostback, it should always trigger my "SearchEvent"
I used an UpdatePanel and an AsyncPostBackTrigger on my CheckBoxlist to call the function in code behind to refresh the dropdowlist.
It works only one time. After the first call, I cannot trigger the CheckBoxlist SelectedIndexChanged, instead I get the error :
"Sys.WebForms.PageRequestManagerServerErrorException: An unknown error occurred while processing the request on the server. The status code returned from the server was: 404"
My dropdownlist also lose the PostBack, nothing happens.
The View ASPX :
<td>
<asp:ScriptManager ID="ScriptManager" runat="server" />
<asp:CheckBoxList ID="IsActiveFilterCheck" runat="server" AutoPostBack="true" AppendDataBoundItems="true" CausesValidation="False">
<asp:ListItem Text="Active" Value="1" />
<asp:ListItem Text="Closed" Value="0" />
</asp:CheckBoxList>
</td>
<td>
<asp:UpdatePanel ID="UpdatePanel1" ChildrenAsTriggers="true" UpdateMode="Conditional" runat="server">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="IsActiveFilterCheck" EventName="SelectedIndexChanged" />
</Triggers>
<ContentTemplate>
<br /><br />
<asp:DropDownList ID="StatusFilterList" runat="server" DataTextField="Name" DataValueField="Id">
</asp:DropDownList>
</ContentTemplate>
</asp:UpdatePanel>
</td>
My code behind :
private void Page_Load(object sender, System.EventArgs e)
{
RegisterCallbacks();
if (!IsPostBack)
{
Initialize();
}
}
override protected void OnInit(EventArgs e)
{
// CODEGEN: This call is required by the ASP.NET Web Form Designer.
CheckProfil();
InitializeComponent();
base.OnInit(e);
}
private void InitializeComponent()
{
this.SearchButton.ServerClick += new System.EventHandler(this.SearchButton_ServerClick);
this.StatusFilterList.SelectedIndexChanged += new System.EventHandler(this.SearchButton_ServerClick);
this.IsActiveFilterCheck.SelectedIndexChanged += new System.EventHandler(this.IsActiveFilterCheck_Changed);
this.Load += new System.EventHandler(this.Page_Load);
}
protected void IsActiveFilterCheck_Changed(object sender, EventArgs e)
{
// Update the Status Filter List
StatusFilterList.Items.Clear();
if (IsActiveFilterCheck.Items.Cast<ListItem>().Where(li => li.Selected).ToList().Count != 1)
{
BindListInsertAll(StatusFilterList, ExpectedStatusCollection.Instance.GetAll());
}
else
{
IList statusSelected = ExpectedStatusCollection.Instance
.GetAll().Cast<ExpectedStatusDo>()
.Where(exp => IsActiveFilterCheck.SelectedValue == "1" ? exp.Id != 5 && exp.Id != 6 : exp.Id == 5 || exp.Id == 6)
.ToList(); // Only Dead and Signed
// Update the Status
BindListInsertAll(StatusFilterList, statusSelected);
}
UpdatePanel1.Update();
//FindByFilter();
}
When I change the IsActiveFilterCheck checkboxlist I should update only the StatusFilterList as shown in the function IsActiveFilterCheck_Changed, without reloading the full page.
This StatusFilterList should always be able to call/Trigger the event SearchButton_ServerClick
Right now It works only one time when the IsActiveFilterCheck is fired my dropdowlist is updated but after when I click anywhere I get the error and I can't trigger the IsActiveFilterCheck

Take a look to this :
AsyncPostBackTrigger works only the first time
People usually recreates the trigger to work after first time.

Updating CSS of Controls in different files via CodeBehind

I have this AJAX button that I want to update some CSS. The problem is that the controls I want it to update are in a different file and can't be moved out of that file.
This is the panel whose CSS I want to update, which is located in the Site.master file:
<asp:ScriptManager ID="ScriptManager" runat="server" />
<asp:UpdatePanel ID="Panel2" runat="server" updatemode="Always">
<ContentTemplate>
<div id="updateThis" runat="server"><p>Test text</p></div>
</ContentTemplate>
</asp:UpdatePanel>
This is the button, located in the Items.ascx file:
<asp:UpdateProgress runat="server" ID="PageUpdateProgress">
<ProgressTemplate>
<img class="ajax-loader" src="/Images/ajax-loader.gif" alt="Loading..." />
</ProgressTemplate>
</asp:UpdateProgress>
<asp:UpdatePanel ID="Panel3" runat="server" updatemode="Conditional">
<Triggers>
<asp:AsyncPostBackTrigger controlid="UpdateButton" eventname="Click" />
</Triggers>
<ContentTemplate>
<asp:Button runat="server" OnClick="UpdateButton"
OnClientClick="hideButton()" Text="Update"
class="update" ID="UpdateButton" name="UpdateButton"
type="submit" ></asp:Button>
</ContentTemplate>
</asp:UpdatePanel>
This is the Items.ascx.cs method that is UpdateButton
protected void UpdateButton(object sender, EventArgs e)
{
var masterPage = this.Page.Master;
var updatePanel = masterPage.FindControl("Panel2");
var div = (HtmlGenericControl)updatePanel.Controls[0].FindControl("updateThis");
div.Style.Add("color", "#ff0000");
}
When I click the button it doesn't end up working correctly. As of right now, with the AJAX UpdateProgress template, it shows the loading GIF and then the GIF disappears and the text never changes color.
EDIT
Hopefully this will give a better idea of where things might be going wrong:
THIS WORKS
protected void UpdateButton(object sender, EventArgs e)
{
var masterPage = this.Page.Master;
var updatePanel = masterPage.FindControl("Panel2");
var div = (HtmlGenericControl)updatePanel.FindControl("updateThis");
div.Style.Add("color", "#ff0000");
UpdateButton.Text = "Done!";
}
I had #updateThis in the FindControl() method. Don't be like me!

You should add the runat="server" attribute to the div control, to make it visible in code-behind:
<div id="updateThis" runat="server"><p>Test text</p></div>
You can also remove Controls[0] in the event handler (but it works if you keep it, according to my tests):
protected void UpdateButton(object sender, EventArgs e)
{
var masterPage = this.Page.Master;
var updatePanel = masterPage.FindControl("Panel2");
var div = (HtmlGenericControl)updatePanel.FindControl("updateThis");
div.Style.Add("color", "#ff0000");
}

Timer in ASP.Net (Language C#) stops after 1 tick

i wanted to use a timer in a program i'm working on, but it always stops after 1 tick !! can you give me any tips to make it repeat unstoppably (or until i want it to) please ??
this is my code:
int i = 20;
protected void Page_Load(object sender, EventArgs e)
{
Label1.Text = "(20)";
}
protected void Timer1_Tick(object sender, EventArgs e)
{
i--;
Label1.Text = "(" + i + ")";
if (i == 0)
{
Session["Profession"] = "Visiteur";
Response.Redirect("Acceuil.aspx");
}
Edit: my HTML code :
<form id="form1" runat="server">
<div><center>
<span class="style1">message</span><br
class="style1" />
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:Timer ID="Timer1" runat="server" Interval="1000" ontick="Timer1_Tick" >
</asp:Timer>
<asp:Timer ID="Timer2" runat="server" Interval="1000">
</asp:Timer>
<br />
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:Label ID="Label1" runat="server"></asp:Label>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Timer1" EventName="Tick" />
</Triggers>
</asp:UpdatePanel>
<asp:LinkButton ID="LinkButton1" runat="server" onclick="LinkButton1_Click"
PostBackUrl="~/Acceuil.aspx">Retour</asp:LinkButton>
<br />
</center>
</div>
</form>
Edit2: what i want to do is the normal redirecting code, count to 20 and refreshing every second (to show to user how much secs left) and at the end it redirects to a new page, but it wasn't working, so i was wondering why ??
and i think i got my answer from #Andrei Rînea, and thank you everyone for your help : )
Edit3: Solved and here is the code :
static int i = 20;
protected void Page_Load(object sender, EventArgs e)
{
if(!Page.IsPostBack)
Label1.Text = "20";
}
protected void Timer1_Tick(object sender, EventArgs e)
{
i--;
Label1.Text = i.ToString();
if (i == 0)
{
i = 20;
Session["Profession"] = "Visiteur";
Response.Redirect("Acceuil.aspx");
}
}
Thanks everyone again : )

Please use the following code :
static int i = 20;
protected void Page_Load(object sender, EventArgs e)
{
if(!Page.IsPostBack)
Label1.Text = "(20)";
}
protected void Timer1_Tick(object sender, EventArgs e)
{
i--;
Label1.Text =i.ToString();
if (i == 0)
{
Session["Profession"] = "Visiteur";
Response.Redirect("Acceuil.aspx");
}
}
your HTML code should be like :
<form id="form1" runat="server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Timer ID="Timer1" runat="server" ontick="Timer1_Tick" Interval="1000">
</asp:Timer>
</ContentTemplate>
</asp:UpdatePanel>
</div>
</form>

I'm going to assume here that you are wishing to have a process that ticks away on your server in the background.
I'm also going to assume you've tried to add this to your Webform.
If so, the issue you have encountered, is that your Webform object only exists for the short time that it is processing your request, after which it is disposed of - including your timer.
If I'm correct, you'd probably like to take a look at Quartz.Net:
http://www.mikesdotnetting.com/article/254/scheduled-tasks-in-asp-net-with-quartz-net

You are trying to run client side code on the server. You need to do this in JavaScript instead.
The C# code will be run just before rendering the page and not longer. You probably believe the code will run as long as the visitor is on the page which is not the case.

How to pass variable from textbox to code behind back to same page

I have a webs form page and I have a text box which once clicked passes a variable to the code behind and then back into another element of that page and I cannot get it to work.
This is the closest I have got.
<asp:Panel ID="Search" runat="server" Visible="true">
<tr>
<td>
<asp:Label ID="lblSearch" runat="server" Text="Search"></asp:Label>
</td>
<td>
<asp:TextBox ID="search" runat="server" />
</td>
<td>
<asp:RequiredFieldValidator ID="valSearch" runat="server"
ControlToValidate="movieSearch" Text="Please enter text" />
</td>
<td>
<asp:Button ID="btnSubmit" runat="server" Text="Save"
OnClick="btnSubmit_Click" />
</td>
</tr>
</table>
</asp:Panel>
<asp:Panel ID="pnlSearchResult" runat="server" Visible="false">
<script>
var search = '<%=Server.UrlDecode(Request.QueryString["Data"]) %>';
</script>
</asp:Panel>
And the code behind:
protected void btnSubmit_Click(object sender, EventArgs e)
{
if (IsValid)
{
pnlSearch.Visible = false;
pnlSearchResult.Visible = true;
Response.Redirect("search.aspx?Data=" + Server.UrlEncode(search.Text));
}
}
Also this does not change the visibility of the two panels for some reason.
I would appreciate any guidance I am very new to asp and c#.

The panel's visibility is not changing because you're forcing a new GET request to the page with this: -
Response.Redirect("search.aspx?Data=" + Server.UrlEncode(search.Text));
(I'm assuming your page is called 'search.aspx')
There's no need to do this. Remove this line.
Secondly, I see you want to force the textbox's Text value into a Javascript variable. Replace this
var search = '<%=Server.UrlDecode(Request.QueryString["Data"]) %>';
with this
var search = '<%= search.Text %>';

Write below code on page event.
Another more important point is you first panel Id is "Search" not "pnlSearch" on aspx page so please correct it
protected void Page_Load(object sender, EventArgs e)
{
if (Request.QueryString["Data"] != null)
{
Search.Visible = false;
pnlSearchResult.Visible = true;
}
}

I recommend solution without using Response.Redirect.
Code Behind Submit Button click:
protected void btnSubmit_Click(object sender, EventArgs e)
{
if (IsValid)
{
pnlSearch.Visible = false;
pnlSearchResult.Visible = true;
}
}
In Markup:
<asp:Panel ID="pnlSearchResult" runat="server" Visible="false">
<script>
var searchTxt = document.getElementById('search');
if(searchTxt.value != null && searchTxt.value != ''){
//do your stuff
}
</script>

Showing buttons if list view is empty

I have a list view which retrieves the data from sql data source. I am trying to make two buttons(Yes and No) and a label outside the list view visible only if the list view is not empty. The process is: a person enter the information into text boxes and click the button retrieve, if the entered data exists in the database, the list view shows certain information.
I have the following code:
protected void btnExistingRetrive_Click(object sender, EventArgs e)
{
if (lstExisting.Items.Count>0 )
{
lblIsITYou.Visible = true;
btnYes.Visible = true;
btnNo.Visible = true;
}
}
By default buttons and the label are not visible.
The problem is when i click on retrieve button it shows me the list view with the information but buttons a the label are still not visible. They became visible only when i double click the retrieve button. Please tell me what is my mistake?
Thank you

Use the ListView EmptyDataTemplate
<asp:ListView ID="ContactsListView"
DataSourceID="ContactsDataSource"
runat="server">
<LayoutTemplate>
<table runat="server" id="tblProducts">
<tr runat="server" id="itemPlaceholder" />
</table>
</LayoutTemplate>
<ItemTemplate>
<tr runat="server">
<td>
<asp:Label ID="FirstNameLabel" runat="Server" Text='<%#Eval("FirstName") %>' />
</td>
<td>
<asp:Label ID="LastNameLabel" runat="Server" Text='<%#Eval("LastName") %>' />
</td>
</tr>
</ItemTemplate>
<EmptyDataTemplate>
<table class="emptyTable" cellpadding="5" cellspacing="5">
<tr>
<td>
<asp:Image ID="NoDataImage"
ImageUrl="~/Images/NoDataImage.jpg"
runat="server"/>
</td>
<td>
No records available.
</td>
</tr>
</table>
</EmptyDataTemplate>
</asp:ListView>

do you bind listview before checking the items count?

Do this on postback instead of in the event.
In your Page_Load do something like this:
protected void Page_Load(object sender, EventArgs e)
{
bool visible = (lstExisting.Items.Count > 0); // assuming it's never null
lblIsITYou.Visible = visible;
btnYes.Visible = visible;
btnNo.Visible = visible;
}
If the above creates complications then do as I said first with postback:
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
bool visible = (lstExisting.Items.Count > 0); // assuming it's never null
lblIsITYou.Visible = visible;
btnYes.Visible = visible;
btnNo.Visible = visible;
}
}