The benefit of events??

Hi,

I am trying to determine the best use for custom events.

Here is mytest code. (I know that the arguments are inappropriate for event handlers ... but this is just a test.) The code simply updates a Label control on the webform:

Namespace test
 Public Class events
 Inherits System.Web.UI.Page
 Protected lblMessage As System.Web.UI.WebControls.Label
 Protected Delegate Sub EventHandler( ByRef comment As String )
 Protected Event Event1 As EventHandler
 Protected Sub Page_Init( ByVal sender As System.Object, ByVal eArgs As System.EventArgs ) Handles MyBase.Init
 AddHandler Me.Event1, AddressOf Me.Event1Handler
 AddHandler Me.Event1, AddressOf Me.Event2Handler
 End Sub
 Protected Sub Page_Load( ByVal sender As System.Object, ByVal eArgs As System.EventArgs ) Handles MyBase.Load
 If Not Page.IsPostBack Then
 Dim toSay As String = "raised as event"
 RaiseEvent Event1( toSay )
 RaiseEvent Event1( toSay )
 Event1Handler( "called as method" )
 End If
 End Sub
 Private Sub Event1Handler( ByRef comment As String )
 lblMessage.Text &= "Event1Handler: " & comment
 comment &= ", changed by Event1Handler"
 End Sub
 Private Sub Event2Handler( ByRef comment As String )
 lblMessage.Text &= "Event2Handler: " & comment
 comment &= ", changed by Event2Handler"
 End Sub
 End Class
End Namespace

In terms of functionality, there doesn't seem to be any difference between raising an event [RaiseEvent Event1( "raised as event" )] and "calling" the event handler directly [Event1Handler( "called as method" )].

In my test, they did exactly the same thing. I can see only two benefits to using events.

First, I can dynamically attach one or more methods to an event. This helps in implementing certain design patterns.

Second, a raised event need not be handled at all. Whereas calling a missing method generates an exception, raising a custom event with no handler is okay.

Am I missing the importance of events?Well,

in your example Event1Handler is private method (it is event handler after all).

Generally events should have corresponding protected method <On>EventName which is used to raise the event by calling it.

For example you have :

Protected Event Event1 As EventHandler

which would have corresponding method:

Protected Sub OnEvent1(comment As String)
 RaiseEvent Event1(comment1)
End Sub

which would provide a way for inherited classes to raise the event by calling the inherited method.

OnEvent1("Something")

So it is the inheritance thing in picture as well.

And usually event should always provide the sender of the event (object that raises the event) so that event's consumer would have straight access to the object that is raising the event (another alternative is of course just give enough event arguments)

C# provides a way to check if event has listeners attached so that event wouldn't be raised if there are no listeners (to save some horsepower ;-) ). VB doesn't currently have this feature.

The Command event of dynamically loaded controls

Hi,

I noticed an interesting effect when working with controls that are
dynamically loaded. For instance, on a web form with a PlaceHolder control
named ImageHolder, I dynamically add an image button at runtime:

//-- Code snippet
protected System.Web.UI.WebControls.PlaceHolder ImageHolder;

private void Page_Load(object sender, System.EventArgs e)
{
if (!IsPostBack)
LoadDynamicImageButton();
}

private void ImageButton_Click(object sender,
System.Web.UI.ImageClickEventArgs e)
{
Response.Write("Image button clicked");
}

private void LoadDynamicImageButton()
{
ImageButton btn = new ImageButton();
btn.ImageUrl = "Images/Minus.png";
btn.Click += new ImageClickEventHandler(ImageButton_Click);
ImageHolder.Controls.Add(btn);
}
//-- End code snippet

The first time the page loads, the image button is created. When I click it,
it reloads the page but doesn't trigger its ImageClickEventHandler. If I
forcefully run LoadDynamicImageButton(), i.e., remove the IsPostBack check
in Page_Load() to recreate the image, its ImageClickEventHandler is
triggered. This happens with the Command event as well.

It seems that on post-back, if a dynamically loaded control is not loaded,
then its event handler is not wired. Its properties such as CommandName and
CommandArgument, OTOH, persists from the last load.

The problem is that if I dynamically load up the PlaceHolder control with
different controls according to the button clicked, this behavior forces all
those controls to be loaded twice - first to load all default controls just
to wire up their event handlers, then to reload them again according to the
event. There are also other factors, such as the assigning a differnet
ImageUrl, that seem to affect whether or not the event handler is triggered.
I'm still working on it to hopefully isolate the problem.

Is there a workaround?

Thanks,
Donald XieHi Donald,

Thanks for posting in the community!
From your description, you dynamically add some command controls such as
button or ImageButton into a webform within a placeholder.(in the page_load
event when the page is first loaded). Also, you registered a "Click" event
handler for the dynamicly added control. However, you found that when you
clicked the control , its event handler hadn't been called and if you did
the adding and registering event handler operation every time the page is
loaded in Page_load, it worked well, yes?

I've tested the code you provided and also tried using other controls such
as Button and did encoutnered the same problem. Currently, I am finding
proper resource to assist you and we will update as soon as posible. In the
meantime, if you have any new findings, please feel free to post here.

Regards,

Steven Cheng
Microsoft Online Support

Get Secure! www.microsoft.com/security(This posting is provided "AS IS",
with no warranties, and confers no rights.)
Hi Donald,

This is normal behavior and results from the way ASP.NET remembers the old
value for that text box in order to determine if the new value is different.

Each time the form is sent to the browser, ASP.NET stores the current text
box value (and other controls) in a hidden field which it sends to the
browser. When the browser posts the page back, the hidden field is sent to
the server along with the rest of the form. ASP.NET parses the list of old
values from the hidden field and attempts to associate each value with a
control. Then it compares the new value of the control with the old value
and triggers events.

The text box must be recreated to allow ASP.NET to associate it with the
old value from the hidden field. Only then can ASP.NET compare the new and
old values.

Here is a code sample which demonstrates one text box that correctly
triggers the changed event and three text boxes which fail for each of
three reasons.

**** HTML
<form id="Form1" method="post" runat="server">
<P>This sample contains a series of text boxes added to the page<BR>
programmatically with Controls.Add. The variations in these<BR>
text boxes demonstrate how to (and how not to) add a control<BR>
so that it can fire an event.<BR>
<BR>
</P>
<asp:panel id="Panel1" runat="server">
<P>
<asp:Label id="Label5" runat="server" Width="115px"> With
ViewState:</asp:Label>
<asp:PlaceHolder id="PlaceHolder1"
runat="server"></asp:PlaceHolder>
<asp:Label id="Label1" runat="server" Width="368px"
EnableViewState="False"></asp:Label></P>
<P>
<asp:Label id="Label6" runat="server" Width="115px" Height="19"> No
ViewState:</asp:Label>
<asp:PlaceHolder id="PlaceHolder2"
runat="server"></asp:PlaceHolder>
<asp:Label id="Label2" runat="server" Width="368px"
EnableViewState="False"></asp:Label></P>
<P>
<asp:Label id="Label7" runat="server" Width="115px"
Height="19px">Controls.AddAt:</asp:Label>
<asp:Label id="Label3" runat="server" Width="368px"
EnableViewState="False"></asp:Label></P>
<P>
<asp:Label id="Label8" runat="server" Width="115px"
Height="19px">!IsPostBack:</asp:Label>
<asp:PlaceHolder id="PlaceHolder4"
runat="server"></asp:PlaceHolder>
<asp:Label id="Label4" runat="server" Width="368px"
EnableViewState="False"></asp:Label></P>
</asp:panel>
<P><asp:button id="Button1" runat="server" Text="Submit" Width="100px"
Height="27px"></asp:button></P>
<P><hr></P>
<P>As you can see through experimenting with the above, the text<BR>
box labeled "With ViewState" is the only one that works properly.<BR>
<BR>
The "No ViewState" and the "Controls.AddAt" text boxes both<BR>
fire their changed events whenever they contain text, even if that<BR>
text has not changed.<BR>
<BR>
The "!IsPostBack" text box simply disappears upon postback.</P>
</form
**** CODE
private void Page_Load(object sender, System.EventArgs e)
{
System.Web.UI.WebControls.TextBox MyTextBox;

MyTextBox = new TextBox();
MyTextBox.ID = "TextBox1";
MyTextBox.EnableViewState=true;
PlaceHolder1.Controls.Add(MyTextBox);
MyTextBox.TextChanged += new
System.EventHandler(this.TextBox_TextChanged);

MyTextBox = new TextBox();
MyTextBox.ID = "TextBox2";
MyTextBox.EnableViewState=false;
PlaceHolder2.Controls.Add(MyTextBox);
MyTextBox.TextChanged += new
System.EventHandler(this.TextBox_TextChanged);

MyTextBox = new TextBox();
MyTextBox.ID = "TextBox3";
MyTextBox.EnableViewState=true;
Panel1.Controls.AddAt(15,MyTextBox);
MyTextBox.TextChanged += new
System.EventHandler(this.TextBox_TextChanged);

if(!IsPostBack)
{
MyTextBox = new TextBox();
MyTextBox.ID = "TextBox4";
MyTextBox.EnableViewState=true;
PlaceHolder4.Controls.Add(MyTextBox);
MyTextBox.TextChanged += new
System.EventHandler(this.TextBox_TextChanged);
}
}

private void TextBox_TextChanged(object sender, System.EventArgs e)
{
TextBox txtBoxSender = (TextBox)sender;
string strTextBoxID = txtBoxSender.ID;

switch(strTextBoxID)
{
case "TextBox1":
Label1.Text = "Changed";
break;
case "TextBox2":
Label2.Text = "Changed";
break;
case "TextBox3":
Label3.Text = "Changed";
break;
case "TextBox4":
Label4.Text = "Changed";
break;
}
}

--
Please see these articles for more information.

Adding Controls to a Web Forms Page Programmatically
http://msdn.microsoft.com/library/e...gcontrolstowebf
ormspageprogrammatically.asp

HOW TO: Dynamically Create Controls in ASP.NET by Using Visual C# .NET
http://support.microsoft.com/defaul...kb;EN-US;317794

Does this answer your question?

Thank you, Mike
Microsoft, ASP.NET Support Professional

Microsoft highly recommends to all of our customers that they visit the
http://www.microsoft.com/protect site and perform the three straightforward
steps listed to improve your computers security.

This posting is provided "AS IS", with no warranties, and confers no rights.

-------
> From: "Donald Xie" <donald_xie@dotnet.itags.org.msdn.nospam>
> Subject: The Command event of dynamically loaded controls
> Date: Fri, 30 Jan 2004 16:52:00 +0800
> Lines: 54
> X-Priority: 3
> X-MSMail-Priority: Normal
> X-Newsreader: Microsoft Outlook Express 6.00.2800.1158
> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165
> Message-ID: <#C2U35w5DHA.2580@dotnet.itags.org.TK2MSFTNGP11.phx.gbl>
> Newsgroups: microsoft.public.dotnet.framework.aspnet
> NNTP-Posting-Host: 202.181.80.84
> Path:
cpmsftngxa07.phx.gbl!cpmsftngxa10.phx.gbl!TK2MSFTN GXA05.phx.gbl!TK2MSFTNGP08
.phx.gbl!TK2MSFTNGP11.phx.gbl
> Xref: cpmsftngxa07.phx.gbl microsoft.public.dotnet.framework.aspnet:206364
> X-Tomcat-NG: microsoft.public.dotnet.framework.aspnet
> Hi,
> I noticed an interesting effect when working with controls that are
> dynamically loaded. For instance, on a web form with a PlaceHolder control
> named ImageHolder, I dynamically add an image button at runtime:
> //-- Code snippet
> protected System.Web.UI.WebControls.PlaceHolder ImageHolder;
> private void Page_Load(object sender, System.EventArgs e)
> {
> if (!IsPostBack)
> LoadDynamicImageButton();
> }
> private void ImageButton_Click(object sender,
> System.Web.UI.ImageClickEventArgs e)
> {
> Response.Write("Image button clicked");
> }
> private void LoadDynamicImageButton()
> {
> ImageButton btn = new ImageButton();
> btn.ImageUrl = "Images/Minus.png";
> btn.Click += new ImageClickEventHandler(ImageButton_Click);
> ImageHolder.Controls.Add(btn);
> }
> //-- End code snippet
> The first time the page loads, the image button is created. When I click
it,
> it reloads the page but doesn't trigger its ImageClickEventHandler. If I
> forcefully run LoadDynamicImageButton(), i.e., remove the IsPostBack check
> in Page_Load() to recreate the image, its ImageClickEventHandler is
> triggered. This happens with the Command event as well.
> It seems that on post-back, if a dynamically loaded control is not loaded,
> then its event handler is not wired. Its properties such as CommandName
and
> CommandArgument, OTOH, persists from the last load.
> The problem is that if I dynamically load up the PlaceHolder control with
> different controls according to the button clicked, this behavior forces
all
> those controls to be loaded twice - first to load all default controls
just
> to wire up their event handlers, then to reload them again according to
the
> event. There are also other factors, such as the assigning a differnet
> ImageUrl, that seem to affect whether or not the event handler is
triggered.
> I'm still working on it to hopefully isolate the problem.
> Is there a workaround?
> Thanks,
> Donald Xie
Thanks for the excellent explanation, Mike. Yes that answers my question.

Now I'm trying to find a good solution for my problem. In a nutshell, I need
to load a hierarchical list of folders and files from a database and display
them on a tree - very much the same as the MSDN Library deeptree.asp. The
number of nodes is potentially large, so I'll only load all top level
folders plus folders in the branch selected by the user. Only one branch can
be expanded each time. My users can click a folder node to expand or
collapse it, based on the selected folder's state.

Since my client doesn't want to use a third party tree control, my first
thought i\was to programmatically create a list of ImageButton/LinkButton
pairs to display the folders. This dynamic control's behavior means that:

1. I'll need to load the folder list in the first pass to wire up the
controls and corresponding event handlers. After it's loaded, the event
handler will fire and give me the selected folder. Then,

2. I'll then load the folder list again with the selected folder
expanded/collapsed.

It doesn't seem like a very efficient solution now because it requires two
trips to the database to load the folder list. Caching doesn't sound very
attractive either because list can be quite big and changes frequently.

Any suggestions are very much appreciated.

Cheers,
Donald Xie

""Mike Moore [MSFT]"" <michmo@dotnet.itags.org.online.microsoft.com> wrote in message
news:AXcHok55DHA.3032@dotnet.itags.org.cpmsftngxa07.phx.gbl...
> Hi Donald,
> This is normal behavior and results from the way ASP.NET remembers the old
> value for that text box in order to determine if the new value is
different.
> Each time the form is sent to the browser, ASP.NET stores the current text
> box value (and other controls) in a hidden field which it sends to the
> browser. When the browser posts the page back, the hidden field is sent to
> the server along with the rest of the form. ASP.NET parses the list of old
> values from the hidden field and attempts to associate each value with a
> control. Then it compares the new value of the control with the old value
> and triggers events.
> The text box must be recreated to allow ASP.NET to associate it with the
> old value from the hidden field. Only then can ASP.NET compare the new and
> old values.
> Here is a code sample which demonstrates one text box that correctly
> triggers the changed event and three text boxes which fail for each of
> three reasons.
>
> **** HTML
> <form id="Form1" method="post" runat="server">
> <P>This sample contains a series of text boxes added to the page<BR>
> programmatically with Controls.Add. The variations in these<BR>
> text boxes demonstrate how to (and how not to) add a control<BR>
> so that it can fire an event.<BR>
> <BR>
> </P>
> <asp:panel id="Panel1" runat="server">
> <P>
> <asp:Label id="Label5" runat="server" Width="115px"> With
> ViewState:</asp:Label>
> <asp:PlaceHolder id="PlaceHolder1"
> runat="server"></asp:PlaceHolder>
> <asp:Label id="Label1" runat="server" Width="368px"
> EnableViewState="False"></asp:Label></P>
> <P>
> <asp:Label id="Label6" runat="server" Width="115px" Height="19"> No
> ViewState:</asp:Label>
> <asp:PlaceHolder id="PlaceHolder2"
> runat="server"></asp:PlaceHolder>
> <asp:Label id="Label2" runat="server" Width="368px"
> EnableViewState="False"></asp:Label></P>
> <P>
> <asp:Label id="Label7" runat="server" Width="115px"
> Height="19px">Controls.AddAt:</asp:Label>
> <asp:Label id="Label3" runat="server" Width="368px"
> EnableViewState="False"></asp:Label></P>
> <P>
> <asp:Label id="Label8" runat="server" Width="115px"
> Height="19px">!IsPostBack:</asp:Label>
> <asp:PlaceHolder id="PlaceHolder4"
> runat="server"></asp:PlaceHolder>
> <asp:Label id="Label4" runat="server" Width="368px"
> EnableViewState="False"></asp:Label></P>
> </asp:panel>
> <P><asp:button id="Button1" runat="server" Text="Submit" Width="100px"
> Height="27px"></asp:button></P>
> <P><hr></P>
> <P>As you can see through experimenting with the above, the text<BR>
> box labeled "With ViewState" is the only one that works
properly.<BR>
> <BR>
> The "No ViewState" and the "Controls.AddAt" text boxes both<BR>
> fire their changed events whenever they contain text, even if
that<BR>
> text has not changed.<BR>
> <BR>
> The "!IsPostBack" text box simply disappears upon postback.</P>
> </form>
>
> **** CODE
> private void Page_Load(object sender, System.EventArgs e)
> {
> System.Web.UI.WebControls.TextBox MyTextBox;
> MyTextBox = new TextBox();
> MyTextBox.ID = "TextBox1";
> MyTextBox.EnableViewState=true;
> PlaceHolder1.Controls.Add(MyTextBox);
> MyTextBox.TextChanged += new
> System.EventHandler(this.TextBox_TextChanged);
> MyTextBox = new TextBox();
> MyTextBox.ID = "TextBox2";
> MyTextBox.EnableViewState=false;
> PlaceHolder2.Controls.Add(MyTextBox);
> MyTextBox.TextChanged += new
> System.EventHandler(this.TextBox_TextChanged);
> MyTextBox = new TextBox();
> MyTextBox.ID = "TextBox3";
> MyTextBox.EnableViewState=true;
> Panel1.Controls.AddAt(15,MyTextBox);
> MyTextBox.TextChanged += new
> System.EventHandler(this.TextBox_TextChanged);
> if(!IsPostBack)
> {
> MyTextBox = new TextBox();
> MyTextBox.ID = "TextBox4";
> MyTextBox.EnableViewState=true;
> PlaceHolder4.Controls.Add(MyTextBox);
> MyTextBox.TextChanged += new
> System.EventHandler(this.TextBox_TextChanged);
> }
> }
> private void TextBox_TextChanged(object sender, System.EventArgs e)
> {
> TextBox txtBoxSender = (TextBox)sender;
> string strTextBoxID = txtBoxSender.ID;
> switch(strTextBoxID)
> {
> case "TextBox1":
> Label1.Text = "Changed";
> break;
> case "TextBox2":
> Label2.Text = "Changed";
> break;
> case "TextBox3":
> Label3.Text = "Changed";
> break;
> case "TextBox4":
> Label4.Text = "Changed";
> break;
> }
> }
>
> --
> Please see these articles for more information.
> Adding Controls to a Web Forms Page Programmatically
http://msdn.microsoft.com/library/e...gcontrolstowebf
> ormspageprogrammatically.asp
> HOW TO: Dynamically Create Controls in ASP.NET by Using Visual C# .NET
> http://support.microsoft.com/defaul...kb;EN-US;317794
> Does this answer your question?
> Thank you, Mike
> Microsoft, ASP.NET Support Professional
> Microsoft highly recommends to all of our customers that they visit the
> http://www.microsoft.com/protect site and perform the three
straightforward
> steps listed to improve your computers security.
> This posting is provided "AS IS", with no warranties, and confers no
rights.
>
> -------
> > From: "Donald Xie" <donald_xie@dotnet.itags.org.msdn.nospam>
> > Subject: The Command event of dynamically loaded controls
> > Date: Fri, 30 Jan 2004 16:52:00 +0800
> > Lines: 54
> > X-Priority: 3
> > X-MSMail-Priority: Normal
> > X-Newsreader: Microsoft Outlook Express 6.00.2800.1158
> > X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165
> > Message-ID: <#C2U35w5DHA.2580@dotnet.itags.org.TK2MSFTNGP11.phx.gbl>
> > Newsgroups: microsoft.public.dotnet.framework.aspnet
> > NNTP-Posting-Host: 202.181.80.84
> > Path:
cpmsftngxa07.phx.gbl!cpmsftngxa10.phx.gbl!TK2MSFTN GXA05.phx.gbl!TK2MSFTNGP08
> phx.gbl!TK2MSFTNGP11.phx.gbl
> > Xref: cpmsftngxa07.phx.gbl
microsoft.public.dotnet.framework.aspnet:206364
> > X-Tomcat-NG: microsoft.public.dotnet.framework.aspnet
> > Hi,
> > I noticed an interesting effect when working with controls that are
> > dynamically loaded. For instance, on a web form with a PlaceHolder
control
> > named ImageHolder, I dynamically add an image button at runtime:
> > //-- Code snippet
> > protected System.Web.UI.WebControls.PlaceHolder ImageHolder;
> > private void Page_Load(object sender, System.EventArgs e)
> > {
> > if (!IsPostBack)
> > LoadDynamicImageButton();
> > }
> > private void ImageButton_Click(object sender,
> > System.Web.UI.ImageClickEventArgs e)
> > {
> > Response.Write("Image button clicked");
> > }
> > private void LoadDynamicImageButton()
> > {
> > ImageButton btn = new ImageButton();
> > btn.ImageUrl = "Images/Minus.png";
> > btn.Click += new ImageClickEventHandler(ImageButton_Click);
> > ImageHolder.Controls.Add(btn);
> > }
> > //-- End code snippet
> > The first time the page loads, the image button is created. When I click
> it,
> > it reloads the page but doesn't trigger its ImageClickEventHandler. If I
> > forcefully run LoadDynamicImageButton(), i.e., remove the IsPostBack
check
> > in Page_Load() to recreate the image, its ImageClickEventHandler is
> > triggered. This happens with the Command event as well.
> > It seems that on post-back, if a dynamically loaded control is not
loaded,
> > then its event handler is not wired. Its properties such as CommandName
> and
> > CommandArgument, OTOH, persists from the last load.
> > The problem is that if I dynamically load up the PlaceHolder control
with
> > different controls according to the button clicked, this behavior forces
> all
> > those controls to be loaded twice - first to load all default controls
> just
> > to wire up their event handlers, then to reload them again according to
> the
> > event. There are also other factors, such as the assigning a differnet
> > ImageUrl, that seem to affect whether or not the event handler is
> triggered.
> > I'm still working on it to hopefully isolate the problem.
> > Is there a workaround?
> > Thanks,
> > Donald Xie
Hi Donald,

Thank you for the response. Regarding on the issue, we are
finding proper resource to assist you and we will update as soon as posible.

Regards,

Steven Cheng
Microsoft Online Support

Get Secure! www.microsoft.com/security(This posting is provided "AS IS",
with no warranties, and confers no rights.)
Hi Donald,

As for the situation you mentioned in the last reply, here is my
suggestions on it:
1. If we manually build a "tree" programatically via a list of ImageButtons
or LinkButtons, I'm afraid there will cause some performance issues since
every time page loaded , it need to create and add these dynamic controls
so as to associate their states from viewstate, also register the event
handler for them. This will be a large challenge to the serverside.

2. Would you like to have a try on the TreeView control in the Microsoft
Internet Explorer WebControls? This treeview control has been added to the
MS's web control collections and have detailed reference and tutorial in
MSDN. Also, the IE webcontrols' source code is opened to public , you're
feel to extend their existed functions. Here is some tech references and
articls on the TreeView web control:

#TreeView WebControl Reference
http://msdn.microsoft.com/library/e...ingtreeviewiewe
bcontrol.asp?frame=true

And here is a test page I used to test dynamically add nodes when a certain
node is expanded. The treeview has
4 hierarchies and each contains 20 nodes. When a node is first time
expanded or selected, it dynamically add its child nodes. Please have a
look to see whether it possible for you to use this TreeView control.

In addition, if you have the "Application Center Test" installed, you may
try having a test on different approachs such as using TreeView or manually
add button lists so as to see the realtime performance. And here are
another two tech articles, one is about the MSDN site's TreeView 's
implementation in C#. I think they may be helpful to you,too.

#Hierarchical Data Binding in ASP.NET
http://msdn.microsoft.com/library/e...databinding.asp
?frame=true

#The MSDN Table of Contents in C#
http://msdn.microsoft.com/library/e...001.asp?frame=t
rue

Please check out the above suggestions. If you have any questions or if my
suggestions not quite suitable for your situation, please feel free to post
here.

Regards,

Steven Cheng
Microsoft Online Support

Get Secure! www.microsoft.com/security
(This posting is provided "AS IS", with no warranties, and confers no
rights.)
Hi Donald,

Sorry for forgetting attach My test page's code in the last reply, here is
the Page code:
#If you haven't the IE web control's reference or code, you may get them at
http://www.asp.net/ControlGallery/C...l=75&tabindex=2

----------aspx page-----------
<%@dotnet.itags.org. Register TagPrefix="iewc" Namespace="Microsoft.Web.UI.WebControls"
Assembly="Microsoft.Web.UI.WebControls" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>DynaTree</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema"
content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<table width="500" align="center">
<tr>
<td><FONT face="">
<iewc:TreeView id="trvMain"
runat="server"></iewc:TreeView></FONT></td>
</tr>
<tr>
<td></td>
</tr>
</table>
</form>
</body>
</HTML
--------code behind class-----
public class DynaTree : System.Web.UI.Page
{
protected Microsoft.Web.UI.WebControls.TreeView trvMain;

private void Page_Load(object sender, System.EventArgs e)
{
if(!IsPostBack)
{
LoadData();
BindTreeNodes(trvMain.Nodes,GetChildNodes("0"));
trvMain.AutoPostBack = true;
}
}

protected void LoadData()
{
DataTable tb = new DataTable();
tb.Columns.Add("nid");
tb.Columns.Add("pid");
tb.Columns.Add("name");
tb.Columns.Add("url");
tb.Columns.Add("target");

int i=0;
int j=0;
int k=0;
int l=0;
int nodeindex = 1;

for(i=1;i<=20;i++)
{
DataRow row1 = tb.NewRow();
row1["nid"] = i.ToString();
row1["pid"] = "0";
row1["name"] = "FirstLevelNode_"+nodeindex.ToString();
row1["url"] = "";
row1["target"] = "";
tb.Rows.Add(row1);

for(j=1;j<=20;j++)
{

DataRow row2 = tb.NewRow();
row2["nid"] = i.ToString() + j.ToString();
row2["pid"] = i.ToString();
row2["name"] = "SecondLevelNode_"+j.ToString();
row2["url"] = "";
row2["target"] = "";
tb.Rows.Add(row2);

for(k=1;k<=20;k++)
{

DataRow row3 = tb.NewRow();
row3["nid"] = i.ToString() + j.ToString() + k.ToString();
row3["pid"] = i.ToString() + j.ToString();
row3["name"] = "ThirdLevelNode_"+k.ToString();
row3["url"] = "";
row3["target"] = "";
tb.Rows.Add(row3);

for(l=1;l<20;l++)
{
DataRow row4 = tb.NewRow();
row4["nid"] = i.ToString() + j.ToString() + k.ToString() +
l.ToString();
row4["pid"] = i.ToString() + j.ToString() + k.ToString();
row4["name"] = "ForthLevelNode_"+k.ToString();
row4["url"] = "";
row4["target"] = "";
tb.Rows.Add(row4);
}

}
}
}

Session["TEMP_DATA"] = tb;

}

protected DataRow[] GetChildNodes(string pid)
{
DataTable tb = (DataTable)Session["TEMP_DATA"];
DataRow[] rows = tb.Select("pid = '" + pid +"'");

return rows;
}

protected void BindTreeNodes(TreeNodeCollection nodes, DataRow[] rows)
{

for(int i=0;i<rows.Length;i++)
{
TreeNode node = new TreeNode();
node.ID = rows[i]["nid"].ToString();
node.Text = rows[i]["name"].ToString();
node.NavigateUrl = rows[i]["url"].ToString();
node.Target = rows[i]["target"].ToString();

TreeNode emptynode = new TreeNode();
emptynode.ID = node.ID + "#$#EMPTY";

node.Nodes.Add(emptynode);
nodes.Add(node);
}

}

#region Web Form Designer generated code
override protected void OnInit(EventArgs e)
{

InitializeComponent();
base.OnInit(e);
}

private void InitializeComponent()
{
this.trvMain.Expand += new
Microsoft.Web.UI.WebControls.ClickEventHandler(thi s.trvMain_Expand);
this.trvMain.SelectedIndexChange += new
Microsoft.Web.UI.WebControls.SelectEventHandler(th is.trvMain_SelectedIndexCh
ange);
this.Load += new System.EventHandler(this.Page_Load);

}
#endregion

private void trvMain_Expand(object sender,
Microsoft.Web.UI.WebControls.TreeViewClickEventArg s e)
{
TreeNode pnode = ((TreeView)sender).GetNodeFromIndex(e.Node);
TreeNode emptynode = pnode.Nodes[0];

if(emptynode.ID.IndexOf("#$#EMPTY") != -1)
{
pnode.Nodes.Clear();
BindTreeNodes(pnode.Nodes,GetChildNodes(pnode.ID)) ;
}

}

private void trvMain_SelectedIndexChange(object sender,
Microsoft.Web.UI.WebControls.TreeViewSelectEventAr gs e)
{
TreeNode oldnode = ((TreeView)sender).GetNodeFromIndex(e.OldNode);
TreeNode newnode = ((TreeView)sender).GetNodeFromIndex(e.NewNode);

if(newnode.Nodes.Count>0)
{
TreeNode emptynode = newnode.Nodes[0];

if(emptynode.ID.IndexOf("#$#EMPTY") != -1)
{
newnode.Nodes.Clear();
BindTreeNodes(newnode.Nodes,GetChildNodes(newnode. ID));
}
}

}

}
Hi Steven,

Thanks so much for your suggestions and the sample code - they are exactly
the information I need.

The TreeView control is the more conventional, and the MSDN TOC in C# is
very elegant and certainly well proven. I will go through both to see which
is the best for this application.

The hierarchical data binding approach is in essense what I'm doing
manually, as the depth of each node is variable. However I suspect that it
also suffers the same render-twice problem if we want to do more than just
displaying the nodes and get their state on post back.

Best,
Donald Xie

"Steven Cheng[MSFT]" <v-schang@dotnet.itags.org.online.microsoft.com> wrote in message
news:8JbKxSx6DHA.3524@dotnet.itags.org.cpmsftngxa07.phx.gbl...
> Hi Donald,
>
> As for the situation you mentioned in the last reply, here is my
> suggestions on it:
> 1. If we manually build a "tree" programatically via a list of
ImageButtons
> or LinkButtons, I'm afraid there will cause some performance issues since
> every time page loaded , it need to create and add these dynamic controls
> so as to associate their states from viewstate, also register the event
> handler for them. This will be a large challenge to the serverside.
> 2. Would you like to have a try on the TreeView control in the Microsoft
> Internet Explorer WebControls? This treeview control has been added to the
> MS's web control collections and have detailed reference and tutorial in
> MSDN. Also, the IE webcontrols' source code is opened to public , you're
> feel to extend their existed functions. Here is some tech references and
> articls on the TreeView web control:
> #TreeView WebControl Reference
http://msdn.microsoft.com/library/e...ingtreeviewiewe
> bcontrol.asp?frame=true
> And here is a test page I used to test dynamically add nodes when a
certain
> node is expanded. The treeview has
> 4 hierarchies and each contains 20 nodes. When a node is first time
> expanded or selected, it dynamically add its child nodes. Please have a
> look to see whether it possible for you to use this TreeView control.
> In addition, if you have the "Application Center Test" installed, you may
> try having a test on different approachs such as using TreeView or
manually
> add button lists so as to see the realtime performance. And here are
> another two tech articles, one is about the MSDN site's TreeView 's
> implementation in C#. I think they may be helpful to you,too.
> #Hierarchical Data Binding in ASP.NET
http://msdn.microsoft.com/library/e...databinding.asp
> ?frame=true
> #The MSDN Table of Contents in C#
http://msdn.microsoft.com/library/e...001.asp?frame=t
> rue
>
> Please check out the above suggestions. If you have any questions or if my
> suggestions not quite suitable for your situation, please feel free to
post
> here.
>
> Regards,
> Steven Cheng
> Microsoft Online Support
> Get Secure! www.microsoft.com/security
> (This posting is provided "AS IS", with no warranties, and confers no
> rights.)
Hi Donald,

Thanks for your response. I'm glad that my suggestions are helpful to you.
As for the things I mentioned in the last reply, here some of my further
suggestions:
As for the "MSDN TOC in C#", since it is not provided as a Web Server
Control and the DataSource is based on serveral xml files. If you'd like to
use this means, I think you may try dynamically generic the certain XML
files from your own datasource. That'll save your times.

Anyway, which approach to choose all depends on the real time performance.
Hope you'll soon figure out the most appropriate means.

Regards,

Steven Cheng
Microsoft Online Support

Get Secure! www.microsoft.com/security
(This posting is provided "AS IS", with no warranties, and confers no
rights.)

the DataBound event of FormView

hey

asp.net 2.0

I want to programmatically populate (with data from the database) a label
control in a FormView on a webpage.

Is it a good idea to put my logic inside the DataBound event of the
FormView?

any other suggestions?

JeffThe basic databinding pattern with a FormView is the same as with similar
Databound controls such a GridView. Assuming that all your controls (inluding
the label) have their databound field set,

private void BindData()
{
SqlConnection myConnection = new SqlConnection(ConnectionString);
SqlDataAdapter ad = new SqlDataAdapter("SELECT * FROM Users",
myConnection);
DataSet ds = new DataSet();
ad.Fill(ds);
fv1.DataSource = ds;
fv1.DataBind();
FormViewRow row = fv1.Row;

}

You could call the above method inside an if(!Page.IsPostBack) check in your
Page_Load handler.

--Peter
Co-founder, Eggheadcafe.com developer portal:
http://www.eggheadcafe.com
UnBlog:
http://petesbloggerama.blogspot.com
"Jeff" wrote:

Quote:

Originally Posted by

hey
>
asp.net 2.0
>
I want to programmatically populate (with data from the database) a label
control in a FormView on a webpage.
>
Is it a good idea to put my logic inside the DataBound event of the
FormView?
>
any other suggestions?
>
Jeff
>
>
>

Hey Peter!

thanks for your reply!

But I want to manipulate the data returned from the database before I set
display it in the FormView!

Instead of doing this:
<asp:TextBox ID="helloworldTextBox" runat="server" Text='<%#
Bind("helloworld") %>'>
</asp:TextBox><br />

I want to do something like this (in the code behind page):
helloworldTextBox.text = <db value>;

It's an interesting code you sent me, but I have this already configured. I
want to programmatically manipulate the data returned from db before I show
in the label control

Any suggestions?

"Peter Bromberg [C# MVP]" <pbromberg@dotnet.itags.org.yahoo.nospammin.comwrote in message
news:4C96A67E-E381-4F1C-B90B-0CA19F9C9326@dotnet.itags.org.microsoft.com...

Quote:

Originally Posted by

The basic databinding pattern with a FormView is the same as with similar
Databound controls such a GridView. Assuming that all your controls
(inluding
the label) have their databound field set,
>
private void BindData()
{
SqlConnection myConnection = new SqlConnection(ConnectionString);
SqlDataAdapter ad = new SqlDataAdapter("SELECT * FROM Users",
myConnection);
DataSet ds = new DataSet();
ad.Fill(ds);
fv1.DataSource = ds;
fv1.DataBind();
FormViewRow row = fv1.Row;
>
>
}
>
You could call the above method inside an if(!Page.IsPostBack) check in
your
Page_Load handler.
>
>
--Peter
Co-founder, Eggheadcafe.com developer portal:
http://www.eggheadcafe.com
UnBlog:
http://petesbloggerama.blogspot.com
>
>
>
>
"Jeff" wrote:
>

Quote:

Originally Posted by

>hey
>>
>asp.net 2.0
>>
>I want to programmatically populate (with data from the database) a label
>control in a FormView on a webpage.
>>
>Is it a good idea to put my logic inside the DataBound event of the
>FormView?
>>
>any other suggestions?
>>
>Jeff
>>
>>
>>

This is the manipulation I need done to the db data:
String str = reader.GetString(4);
lblInfo.Text = str.Replace(Environment.NewLine, "<br/>");

Maybe I instead could do this data manipulation directly in the stored
procedure (sql server 2005) which returns the datasource to the FormView??

"Peter Bromberg [C# MVP]" <pbromberg@dotnet.itags.org.yahoo.nospammin.comwrote in message
news:4C96A67E-E381-4F1C-B90B-0CA19F9C9326@dotnet.itags.org.microsoft.com...

Quote:

Originally Posted by

The basic databinding pattern with a FormView is the same as with similar
Databound controls such a GridView. Assuming that all your controls
(inluding
the label) have their databound field set,
>
private void BindData()
{
SqlConnection myConnection = new SqlConnection(ConnectionString);
SqlDataAdapter ad = new SqlDataAdapter("SELECT * FROM Users",
myConnection);
DataSet ds = new DataSet();
ad.Fill(ds);
fv1.DataSource = ds;
fv1.DataBind();
FormViewRow row = fv1.Row;
>
>
}
>
You could call the above method inside an if(!Page.IsPostBack) check in
your
Page_Load handler.
>
>
--Peter
Co-founder, Eggheadcafe.com developer portal:
http://www.eggheadcafe.com
UnBlog:
http://petesbloggerama.blogspot.com
>
>
>
>
"Jeff" wrote:
>

Quote:

Originally Posted by

>hey
>>
>asp.net 2.0
>>
>I want to programmatically populate (with data from the database) a label
>control in a FormView on a webpage.
>>
>Is it a good idea to put my logic inside the DataBound event of the
>FormView?
>>
>any other suggestions?
>>
>Jeff
>>
>>
>>

The Global.asax.cs

does anyone know how I would write the event :

Application_BeginRequest

from the Global.asax.cs and put this into my webform as inline code?

I think the event you are looking for is ?

Sub Application_Start(ByVal senderAsObject,ByVal eAs EventArgs)

' Code that runs on application startup

EndSub

Thanks but I need it to fire on every postback, not just on application start-up, so something along the lines of (in c#):

private void Application_BeginRequest(Object Sender, EventArgs e)

{

Response.Write("test");

}

I think its the same name as the event in vb too.

you could create a .cs class that would reside in your App_Code folder and then create your function in it. Then in what ever page you need it you would:

if page.ispostback then

Dim gbFunctionsAsNew globalServerFuncitons // The name of the class

Then gbFunctions.YourFunctionNameInTheClass

end if

I guess I should have explained the problem a little more clearly.. The reason I need this event before the page is requested is because of problem with IIS 5.1 (http://support.microsoft.com/?id=910436)

I am uploading several files using file upload controls but each time a postback occurs (i.e. i submit the form) - i am sent to a dns error page because my file sizes total more than my specified limit in the web config.

I therefore am trying to catch the error before the application requests the file headers and throws you to the very unelegant dns error page as described by the microsoft article above.

SO the example workaround they have given in that article i am trying to incorporate using inline code (not code behind). The reason being is because we use several applications that I am writing the upload component for and my task was to create a single .aspx webform that kept all scripts (c#, javaScript, html) all in the one place so we can easily configure it when re-using in the many other apps we have.

Because of this issue the code will never reach the page load event, only the app start, begin request, and on error of the application (in global). So I need to program one of these into my webform.

Does all the above make sense?

So this error occurs on the client and not the server?

The GridView 'GridView1' fired event Sorting which wasn't handled

Hi,
I get this error message when sorting a gridview:
The GridView 'GridView1' fired event Sorting which wasn't handled
What do I need to do?
Thanks!Hi,
you have AllowSorting="true" set for the GridView and therefore you need to
have event handler for its Sorting event
<asp:GridView AllowSorting=true ID="GridView1" runat="server"
OnSorting="GridView1_Sorting">
..
</asp:GridView>
protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
{
//...
}
Teemu Keiski
ASP.NET MVP, AspInsider
Finland, EU
http://blogs.aspadvice.com/joteke
"Arjen" <boah123@.hotmail.com> wrote in message
news:ddsgue$nbj$1@.news1.zwoll1.ov.home.nl...
> Hi,
> I get this error message when sorting a gridview:
> The GridView 'GridView1' fired event Sorting which wasn't handled
> What do I need to do?
> Thanks!
>
I tried, I don't get it to work.
I don't know what to add inside the GridView1_Sorting method.
I'm using the gridview with templatefields.
Can you help me?
Thanks!
"Teemu Keiski" <joteke@.aspalliance.com> schreef in bericht
news:epu6hdooFHA.1372@.TK2MSFTNGP10.phx.gbl...
> Hi,
> you have AllowSorting="true" set for the GridView and therefore you need
> to
> have event handler for its Sorting event
> <asp:GridView AllowSorting=true ID="GridView1" runat="server"
> OnSorting="GridView1_Sorting">
> ...
> </asp:GridView>
>
> protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
> {
> //...
> }
>
> --
> Teemu Keiski
> ASP.NET MVP, AspInsider
> Finland, EU
> http://blogs.aspadvice.com/joteke
> "Arjen" <boah123@.hotmail.com> wrote in message
> news:ddsgue$nbj$1@.news1.zwoll1.ov.home.nl...
>

The GridView GridView1 fired event Sorting which wasnt handled

Hi,

I get this error message when sorting a gridview:
The GridView 'GridView1' fired event Sorting which wasn't handled

What do I need to do?

Thanks!Hi,

you have AllowSorting="true" set for the GridView and therefore you need to
have event handler for its Sorting event

<asp:GridView AllowSorting=true ID="GridView1" runat="server"
OnSorting="GridView1_Sorting">
...
</asp:GridView
protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
{
//...
}

--
Teemu Keiski
ASP.NET MVP, AspInsider
Finland, EU
http://blogs.aspadvice.com/joteke

"Arjen" <boah123@.hotmail.com> wrote in message
news:ddsgue$nbj$1@.news1.zwoll1.ov.home.nl...
> Hi,
> I get this error message when sorting a gridview:
> The GridView 'GridView1' fired event Sorting which wasn't handled
> What do I need to do?
> Thanks!
I tried, I don't get it to work.
I don't know what to add inside the GridView1_Sorting method.

I'm using the gridview with templatefields.

Can you help me?

Thanks!

"Teemu Keiski" <joteke@.aspalliance.com> schreef in bericht
news:epu6hdooFHA.1372@.TK2MSFTNGP10.phx.gbl...
> Hi,
> you have AllowSorting="true" set for the GridView and therefore you need
> to
> have event handler for its Sorting event
> <asp:GridView AllowSorting=true ID="GridView1" runat="server"
> OnSorting="GridView1_Sorting">
> ...
> </asp:GridView>
>
> protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
> {
> //...
> }
>
> --
> Teemu Keiski
> ASP.NET MVP, AspInsider
> Finland, EU
> http://blogs.aspadvice.com/joteke
> "Arjen" <boah123@.hotmail.com> wrote in message
> news:ddsgue$nbj$1@.news1.zwoll1.ov.home.nl...
>> Hi,
>>
>> I get this error message when sorting a gridview:
>> The GridView 'GridView1' fired event Sorting which wasn't handled
>>
>> What do I need to do?
>>
>> Thanks!
>>
>>