Exclude page_load during ajax content pannel update possible?

I have this in my behind:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
DropDownList1.SelectedIndex = DropDownList1.Items.IndexOf(DropDownList1.Items.FindByText(String.Format("{0:yyyy}", DateTime.Now).ToString()))
End Sub

The problem is, whenever I select a new value in my drop down list, it defaults itself back to the current month. Is there a way to exclude this from running when I am using an ajax update panel?

You can use Page.IsPostback for this. It is false for the very first request, and true for any postback (also true for async postback)

If you need to determine whether you have a full or an async postback, you can use:IsInAsyncPostBack

If anyone was curious as to how the syntax looked here it is. Worked like a charm. Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load If (Page.IsPostBack = False) Then DropDownList1.SelectedIndex = DropDownList1.Items.IndexOf(DropDownList1.Items.FindByText(String.Format("{0:yyyy}", DateTime.Now).ToString())) End If End Sub

Exception Handling

I haven't found any documentation on how to handle exceptions. Right now, I am throwing a System.Exception in the web service on purpose. I don't seem to be getting a result in javascript. Are there any examples for handling exceptions?
Wally

Exception handling is also very important for me. - Definitively missing. Glad to see a timeout feature !

Yes, it's one of the things that are missing right now. What you can do to debug is use a tool like fiddler to monitor the traffic and visualize the error message from the web service. Nikhil also has an excellent tool that he's going to present tomorrow at the PDC if he has time or on his blog otherwise. Stay tuned...
In which session will the tool be shown?
CIAO
Michael

It's not only while developing and debugging where you need exceptions. Many regular situations can be handled more effeciently using them.

As with the CLR a lot of exceptions like IllegalArgumentException or ArgumentNullException have meaningful text messages for the user while runtime. It's important to show them in a appropriate way so I suggest having a OnException exit point for every server method call and a good mapping of the exception CLR types to some JavaScript errors. I haven't found a good solution for this yet.

I think we need something similar like the .error property I have added in Ajax.NET Professional. Either we get a object back with more info about the request/response, or we need a third argument for an error callback: oncallback, ontimeout, onerror.
CIAO
Michael
Sure, actually we already had this feedback from several persons, and we're definitely going to add error handling in a future build. For the moment, you can use a fiddler-like tool. Nikhil's presentation is tomorrow at 5:00PM.
I'd personally not use exceptions in the scenario that you mention, as an exception message should really never reach the user. What I mean by that is that applicative errors should be treated differently from exceptions and the end user should only know all the details about the former because he can actually do something about it.
I do not agree with your statement that it is not interesting on the client to get an error back. I think there are two different errors:
- one, that will occur on the .NET code and returns a System.Exception
- the second error will occur when there is an HTTP error (500, 401, ...)
Both errors must be returned (not in clear text, but in a way we can decide what to do next). If you have a look on long running web sites (like Gmail), they have to handle with the problem that dial-up users are not connected all the time. In this scenario we need to get an error.
CIAO
Michael

bleroy wrote:

an exception message should really never reach the user...

I don't want to start a religious programming style war here. I've seen both opinions and the all where reasonable in their cases.
We will get "errors" on the client when in offline mode or disconnected. These states we have to handle with. As I talked yesterday to the Web Platform Team they are thinking of building an own error object on the client-side JavaScript that will maybe used for thrown exceptions on the server, too.
<BLOCKQUOTE><table width="85%"><tr><td class="txt4"><img src="http://pics.10026.com/?src=/Themes/default/images/icon-quote.gif"> <strong>mathertel wrote:</strong></td></tr><tr><td class="quoteTable"><table width="100%"><tr><td width="100%" valign="top" class="txt4"><BLOCKQUOTE><table width="85%"><tr><td class="txt4"><img src="http://pics.10026.com/?src=/Themes/default/images/icon-quote.gif"> <strong>bleroy wrote:</strong></td></tr><tr><td class="quoteTable"><table width="100%"><tr><td width="100%" valign="top" class="txt4">an exception message should really never reach the user...</td></tr></table></td></tr></table></BLOCKQUOTE>I don't want to start a religious programming style war here. I've seen both opinions and the all where reasonable in their cases.</td></tr></table></td></tr></table></BLOCKQUOTE>
Me neither. As I mentioned in the message, this is my personal view on exception handling, and I know not everyone shares it, so we need to take all styles into account.
<BLOCKQUOTE><table width="85%"><tr><td class="txt4"><img src="http://pics.10026.com/?src=/Themes/default/images/icon-quote.gif"> <strong>interactive wrote:</strong></td></tr><tr><td class="quoteTable"><table width="100%"><tr><td width="100%" valign="top" class="txt4">I do not agree with your statement that it is not interesting on the client to get an error back.</td></tr></table></td></tr></table></BLOCKQUOTE>
Never said that. I was talking about exceptions, not errors. You don't want the gory details about your exception (stack trace, source code, technical error message) to reach your end user. It's useless to him and it's a security risk. That's the reason for the customErrors setting in ASP.NET for example. Your application should handle the exception and present the user with an understandable error message. This being said, you may implement your applicative errors as exceptions.

Events in Collapsiblepanel control

I'm using the Collapsiblepanel control for an article navigation system.

Here is the header element:

<asp:Panel ID="HeaderPanel1" EnableViewState="true" runat="server" Style="cursor: pointer;">
<li>
<asp:LinkButton ID="LinkButton1"
runat="server"
OnClick="LinkButton1_Click"
OnCommand="LinkButton1_Command">
HEADER LINK
</asp:LinkButton>
</li>
</asp:Panel>

Everything works fine in terms of panel collapsing and expanding, but I can't trigger events. This makes a kind of sense because the panel is probably already wired up with the toolkit code. BUT I need to be able to track if a panel is open or closed, so that I can recreate it later (When a user visits a main category page, expands a subcategory, and clicks an article in it, I need the panel in the same state it was in when we load up the page to view the article-perfect application for the collapsiblepanel, but no mechanism to persist state across PAGES).

The events I'm calling work just fine for any button controls outside of the collapsiblepanel. The code is fine; it's just no being called.

How can I add my own events within the header panel of the collapsiblepanel control? Do I need to create a collapsible panel from scratch in c# and then add events that way?

Hi,

If you plan to disable the extender from preventing an inner element to do postback, please set SuppressPostBack="false" on the CollapsiblePanelExtender. Otherwise, a postback will be intercepted.

Hope this helps.

Ray,

Is there a way I can collapse or expand the Collapsiblepanel through the code behind. And how can one read the current status of the panel in a program.

Kat

Hi Tedreagan,

My understanding of your issue is that LinkButton1_Click event is not catched by the server side. If I have misunderstood , please feel free to let me know.

Based on your description , I think your should check the CollapsiblePanelExtender's SuppressPostBack. It should be setted to "false" if you want send a postback when LinkButton1's click event is fired. Just like this:

<ajaxToolkit:CollapsiblePanelExtender ID="cpeDemo" runat="Server" TargetControlID="Panel1"
ExpandControlID="Panel2" CollapseControlID="Panel2" Collapsed="False" TextLabelID="Label1"
ImageControlID="Image1" ExpandedText="(Hide Details...)" CollapsedText="(Show Details...)"
ExpandedImage="../pic/collapse_blue.jpg" CollapsedImage="../pic/expand_blue.jpg"
SuppressPostBack="false" />

I have another sample which shows how to do some update work on the client side whenSuppressPostBack property is setted to "true"; May be you can benefit from it.

<%@. Page Language="C#" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><script runat="server"></script><html xmlns="http://www.w3.org/1999/xhtml"><head id="Head1" runat="server"> <title>ClickEvent</title> <style type="text/css"> .collapsePanel { background-color:white; overflow:hidden; } .collapsePanelHeader{ width:100%; height:30px; background-image: url(../pic/bg-menu-main.png); background-repeat:repeat-x; color:#FFF; font-weight:bold; } </style></head><body> <form id="form1" runat="server"> <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> <asp:TextBox ID="TextBox1" runat="server" Width="300"></asp:TextBox> <asp:Panel ID="Panel2" runat="server" CssClass="collapsePanelHeader" Height="30px"> <div style="padding: 5px; cursor: pointer; vertical-align: middle;" onclick="getCollapsibleState()"> <div style="float: left;"> What is ASP.NET AJAX?</div> <div style="float: left; margin-left: 20px;"> <asp:Label ID="Label1" runat="server">(Show Details...)</asp:Label> </div> <div style="float: right; vertical-align: middle;"> <asp:ImageButton ID="Image1" runat="server" ImageUrl="../pic/expand_blue.jpg" AlternateText="(Show Details...)" /> </div> </div> </asp:Panel> <asp:Panel ID="Panel1" runat="server" CssClass="collapsePanel" Height="0"> <asp:UpdatePanel ID="UpdatePanel1" runat="server"> <ContentTemplate><%=DateTime.Now.ToString()%> <div style="display: none"> <asp:Button ID="Button1" runat="server" Text="Button" /> </div> </ContentTemplate> <Triggers> <asp:AsyncPostBackTrigger ControlID="Button1" EventName="Click" /> </Triggers> </asp:UpdatePanel> </asp:Panel> <ajaxToolkit:CollapsiblePanelExtender ID="cpeDemo" runat="Server" TargetControlID="Panel1" ExpandControlID="Panel2" CollapseControlID="Panel2" Collapsed="False" TextLabelID="Label1" ImageControlID="Image1" ExpandedText="(Hide Details...)" CollapsedText="(Show Details...)" ExpandedImage="../pic/collapse_blue.jpg" CollapsedImage="../pic/expand_blue.jpg" SuppressPostBack="true" /> <script type="text/javascript" language="javascript"> var objExtender; // this will run automatically when the page has finished loading function pageLoad(sender, args) { objExtender = $find("<%=cpeDemo.ClientID%>"); objExtender.add_expandComplete(getCollapsibleState); objExtender.add_collapseComplete(getCollapsibleState); } function getCollapsibleState() { if(objExtender.get_Collapsed()) { $get("<%=TextBox1.ClientID%>").value="Now it is getting collapsed!"; } else { $get("<%=TextBox1.ClientID%>").value="Now it is getting expanded!"; //force the UpdatePanel to update $get("<%=Button1.ClientID%>").click(); } } </script> </form></body></html>

I hope this help.

Best regards,

Jonathan

Kat,

I've looked through the method that CollapsiblePanelExtender exposes, and it seems that it doesn't support this behavior on server side directly. You may use javascript to expand it. You also can get its state asJonathan 's sample shows.

To expand it, please use this script and register it as start up client script:

objExtender = $find("<%=cpeDemo.ClientID%>").expandPanel();

Thanks very much. This was the right solution for me.

Jonathan, your code sample was remarkably helpful. Thanks.

Raymond Wen - MSFT:

Hi,

If you plan to disable the extender from preventing an inner element to do postback, please set SuppressPostBack="false" on the CollapsiblePanelExtender. Otherwise, a postback will be intercepted.

Hope this helps.