Web Forms :: When To Wire Up Event Handlers For Dynamically Loaded User Controls
Jul 15, 2010
I have a situation where I dynamically load one of twenty user controls at a time in an ASP.net web page. Based on much reading I've done, I understand that I am to reload the user control upon postback via the Page_Init event handler. This I've done and it seems to work fine.
But now I would like to wire up assorted controls in the user controls such that when the value of each is changed, an event is fired and the web page is notified. Here's an example of how I'm doing that:
userControl.NewData_Handler += new EventHandler(UserControl_NewData_Handler);
There's a problem though. Because the user control is being done in Page_Init (ie. before Page_Load) I don't believe that a line of code such as the one above can function yet.
So I'm wondering what the best practice to do this is. It occurred to me that perhaps I could execute the line in the Page_Load event handler but I'm not sure if that's correct or not.
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Jun 30, 2010
I was wondering if anyone had an easy way to wire up javascript event handlers to events happening on the server-side. I have a long running process that includes a lot of steps, and would like the client to be continually updated with new information as the steps transition. Will this involve some sort of polling mechanism?
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Mar 11, 2011
I have a aspx page, default.aspx, with an user control in it. Inside the user control (UC 1) there is a DataGrid. When the DataGrid is loading data with ItemDataBound, I need to dynamically load another user control (UC 2) for each row in the DataGrid. UC 2 has a Button ( BTN )with an eventhandler associated with it in code behind.
User control loading is fine, and the Button, BTN, is there. However, when I click the Button, the eventhandler is not reached, not firing, even though the page does postback. I googled for this issues, and I know the dynamically loaded user controls need to be loaded every time the page is postback. In my case, it needs to be loaded each time the datagrid is doing ItemDataBound. I did it and even hook up the eventhandler with button click event each time when the user control is dynamically loaded. I set EnableViewState to true on the Page and controls.
The following is part of the code from UC 1, AcctPaymentDetail is UC 2 in the code.
[Code]....
And the following is UC 2 the is being loaded:
[Code]....
[Code]....
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Mar 22, 2010
reading on the forums about assigning event handlers to controls that are dynamically created via code and am just not getting anywhere.In my particular case, I'm rolling through a directory of images and creating ImageButton controls on the fly and want to assign the OnCommand event to a single handler.Then, by using the CommandName (which is different for each control) I can figure out which ImageButton was clicked and act accordingly.
The snippet below (which can be found in many posts on this topic) is inside a foreach which loops through the directory and gets each FileInfo (fi).Each is then added to a PlaceHolder (phImages).
[Code]...
This code compiles and runs but the event handler is never invoked when an ImageButton is clicked. I believe this is because you cannot, without some coding I'm not familiar enough to do yet, assign a handler to multiple controls.I say this because I ran into a similar problem in a Silverlight app I wrote and had to use a lambda (=>) operator to do something similar (although I admit to not knowing enough about this to know if this situation is the same).
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Feb 27, 2011
I have a user control that is dynamically added to a placeholder control inside an update panel in my main page. The user control has a linkbutton where I try to handle its Command event. The first time the link button is clicked after the user control loads, the form posts back but the command event handler does not execute, although the user control is still on the screen. The second and subsequent times the link button is clicked it works perfectly. When the user control first loads and I mouse over the link button, the browser status bar says: javascript: __doPostBack('ctl08$lbTest',''). After the first click, when I mouseover the link button the browser status bar shows javascript:__doPostBack('ctl07$lbTest',''). Why the changed in id, I can't figure but it must be why it is not hitting the event handler the first time it's clicked. Here is the cs code that loads the user control:
[Code]....
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Jun 11, 2012
trigger dynamically loaded usercontrols click event?
What i did.........Created User Control like One.ascx with one button
<%@ Control Language="C#" AutoEventWireup="false" CodeFile="one.ascx.cs" Inherits="one" %>
<asp:Label ID="Label1" runat="server" Text="Hello, this is My First User Control dynamically loaded :)">
</asp:Label><asp:Button ID="btnShow" runat="server" Text="Show" OnClick="btnShow_Click" />
On Code behind public void btnShow_Click(object sender, EventArgs e) {
[Code] .....
Fail to redirect user to google.com by clicking button which written in .ascx file.
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Jul 31, 2010
I have a blank user control (child) and during Page_Load i create some text boxes and a button. I also add an event to the button.
I then load that user control dynamically from a placeholder in another usercontrol (parent). Both controls are rendered correctly but when i click on the button, the event isnt fired. how to handle the event?
Child code:
[code].....
If i use the child control directy (ie without the parent the control) the click event is raised and handled nicely. But when i use the parent control, the debugger wont even hit a breakpoint inside UpdateButton_Click().
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Dec 24, 2010
I have a dynamically loaded usercontrol
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="ucEditPanel.ascx.cs"
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Feb 7, 2010
I'm developing an ASP.NET application with C# and Ajax.I have a page that holds user controls loaded dynamically. I need to pass some data (integer values and some strings) to the user control that has been loaded dynamically.Now I use Session to pass these values, but I think I can use another way; something like VIEWSTATE or hidden input.What do you recommend me?The fact that I load the controls dynamically is important because controls are loaded on every postback, and I can't store any value on controls.
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Jul 31, 2010
I have created a web user control (MemberDetails.ascx) which is loaded dynamically on a page (Member.aspx) for my website. The control has some TextBoxes. I want to store the values inputted by a user in these TextBoxes to a database on the click event of a button that is on the Member.aspx page (i.e. not a part of user control).
I'll use a small code for example.
Member.ascx page:
[Code]....
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Sep 19, 2010
I load the content of some User Controls into my page with the use of jQuery. So I have this function that extracts the content from my User Control, and it works like a charm.
public string GetObjectHtml(string pathToControl)
{
// Create instance of the page control
Page page = new Page();
// Create instance of the user control
UserControl userControl = (UserControl)page.LoadControl(pathToControl);
//Disabled ViewState- If required
userControl.EnableViewState = false;
//Form control is mandatory on page control to process User Controls
HtmlForm form = new HtmlForm();
//Add user control to the form
form.Controls.Add(userControl);
//Add form to the page
page.Controls.Add(form);
//Write the control Html to text writer
StringWriter textWriter = new StringWriter();
//execute page on server
HttpContext.Current.Server.Execute(page, textWriter, false);
// Clean up code and return html
string html = CleanHtml(textWriter.ToString());
return html;
}
But I would really like to send in some parameters into my User Control when I create it. Is this possible, and how can i do that?
I can see that LoadControl() can take some parameters with object[] parameters but im really not sure on how to use it.
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Mar 14, 2011
For a "dashboard" module I need to dynamically load user controls based on criteria as the user enters the page (role, etc). The problem is that the events are not being fired at all from the controls
As I understand it I need to load the controls in the OnPreInit method of the dashboard page, however I cannot get a reference to the Placeholder control at this point of initialization (i.e. I get a NullReferenceException); trying to load the Placeholder dynamically via Page.FindControl gives me, ironically, a StackOverflowException.
I've tried loading the controls in PreRender and OnInit as well but the events in the controls are not wired up properly and will not fire.
The code is basically this:
[code]....
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Aug 16, 2010
I am following on my own solution to triggering fancybox from asp.net code-behind as here:
http://forums.asp.net/p/1577730/3966910.aspx
But this time I am stuck because my hidden_link control exists inside a dynamically loaded user control, and I do not know it's id, as the id's change to something like this:
ctl00_ContentPlaceHolder1_ctl01_hidden_link2
ctl00_ContentPlaceHolder1_ctl02_hidden_link2
ctl00_ContentPlaceHolder1_ctl03_hidden_link2
I am using
Literal1.Text = "<script>jQuery(document).ready(function() {$("a[id$='hidden_link2']").trigger('click');});</script>";
(which would find an <a> tag ending with hidden_link2) but this only triggers the fancybox for the first user control. How can I inject this script for the required <a> link only? Hope that makes sense.
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May 13, 2010
I have a simple user control containing two text boxes which I am adding to placeholder on Button Click event. I am storing the number(count) of clicks in View state and running a loop using count to create all previously added user control. I am also adding IDs to each User control (appending "UC" and count). I have also checked in view source the ids are same each time they are created. I have another button which basically does an post back. I have EnableViewState enabled ="true" in all controlls all the way up to Page Level. My problem is that User Input does not persist on postback. Should this not be happening automatically for me?
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Oct 9, 2010
In a page , when I click a button 'showDialog' I am loading the user control dynamically in a dialog. I am linking to the event in the user control as explained below. The parent page is not receiving this event.
Button_Click(){
UseControl1 gc = dlg.LoadContent(:UserControl1.csx);
gc.CausePostback += new EventHandler(execute_CausePostback());}
execute_CausePostback(){
In UserControl class after clicking the submit button
Submit_Click(){
saveRecord();
raise event CausePostBack();
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Nov 5, 2010
I have created a user control that contains two asp calendar controls. I need to add this user control twice on the same asp page, let's say for Check in date and Check out date. Since the two are conflicting to each other when I add it twice statically, I now dynamically add them on button click so that each time only one control is loaded. The problem is, when I select a date on a calendar, it seems that the selection event is not happening at all. Of course, I am not getting any date.
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Oct 26, 2010
My main file is messages.aspx and i am loading a UC names message_inbox.ascx dynamically as:
SiteUserControls_Message_MessageInbox InboxUC = Page.Load("message_inbox.ascx") as
SiteUserControls_Message_MessageInbox
Now in my user control ("message_inbox.ascx") i have a various events which i am combining in one group event :
public void ForwardLinkButton_OnClick(object sender, EventArgs e)
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Jun 17, 2013
I have a tab control on my page and on click of tab user control is loaded dynamically.I need to load the javascript file of that user control dynamically. I don't want to add the reference of my js file on parent page.so in my .ascx page load event i added:
System.Web.UI.HtmlControls.HtmlGenericControl js = new System.Web.UI.HtmlControls.HtmlGenericControl("script");
js.Attributes["type"] = "text/javascript";
js.Attributes["src"] = "../../js/DatesJavaScript.js";
Page.Header.Controls.Add(js);
but it is not working.
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Nov 24, 2010
The textbox has an onblur event (the workings of the onblur event are irrelevant), and an associated RequiredFieldValidator. This code functions exactly as it should. However,if in the body onload event I simply raise an alert of the innerHTML of tr1 or td1, the onblur event does not appear (but it does work, and can be seen when I view source in IE7). If I remove the RequiredFieldValidator, the onblur event handler is shown in the alert, or if I retain the validator but change onblur to onfocus, then the event handler also appears in the alert. I need this to work as when the user increases the Quantity, duplicates of the table row are added (I have tried both cloneNode, and setting the innerHTML of each new table cell to that of the original, but as my alert proves, the onblur event handler is not included in what is copied). The same problem also occurs with onchange for select tags with validators. I am using Visual Studio 2008 (.Net
2), IE7 and IIS 7.
[Code]....
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Feb 20, 2011
Hosting page:
protected void Page_Load(object sender, EventArgs e)
{
LoadMyControl(Parameters); //Do it every page load to preserve it's state
}
protected void LoadMyControl(string parameters)
{
plchld.Controls.Clear();
Control userControl = LoadControl("TheUserControl.ascx");
userControl.ID = "userControl1";
plchld.Controls.Add(userControl);
}
Now inside this control, when a button is clicked I want to update ,let's say a Label on the hosting page.
What is the best way to do it? Custom event?
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Feb 12, 2010
I have a problem with ViewState. I have an aspx page that has a treeview on the left and an UpdatePanel with an ASP.NET Panel inside on the right. It is in that inner Panel where I load and unload dynamically user controls. I use that update panel to load dynamically controls.
I also made a custom control for my user controls because I need to pass some values from page. On that constructor I use ViewState to store these values.
The first time I load the user control I call its constructor with parameters. When I reload that user control on each postback I use its normal constructor.
My problem is I the values I've stored on ViewState has become null on successive postback.
Update:
This is a piece of my user control:
public class MyUserControl : System.Web.UI.UserControl
{
private int PKId
{
get { return ViewState["pkId"] as int; }
set { ViewState["pkId"] = value; }
}
public MyUserControl(int pkId)
{
this.PKId = pkId;
}
...
}
I'm following this article to load controls dynamically: http://msdn.microsoft.com/en-us/magazine/cc748662.aspx#id0070065.
Second Update:
I also set the same control ID when I load the user control at first time and on each reaload.
Maybe I can use another method to store these values like input hidden fields or Cache. I've choosen ViewState because I don't want to overload server with Session values for each user.
Third update:
I load the controls with this code:
System.Web.UI.UserControl baseControl = LoadControl(ucUrl) as System.Web.UI.UserControl;
if (baseControl != null)
{
baseControl.ID = "DestinationUserControl";
PanelDestination.Controls.Add(baseControl);
}
And reaload with this code:
DynamicControls.CreateDestination ud = this.LoadControl(TrackedUserControl) as DynamicControls.CreateDestination;
if (ud != null)
{
ud.ID = "DestinationUserControl";
PanelDestination.Controls.Add(ud);
}
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Feb 23, 2010
I have user control that inherits a base control class and these user controls are loaded using the LoadControl method, I can't seem to figure out how to raise events from user controls to the page that are dynamically loaded this way. Here is the delegate and event in the base user control class.
public delegate void SomeChangeEventHandler(object sender
, SomeChangeEventArgs e);
public event SomeChangeEventHandler SomeChangeEvent;
public virtual void OnSomeChanged(SomeChangeEventArgs e)
{
if (SomeChangeEvent != null)
{
SomeChangeEvent(this, e);
}
}
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Dec 13, 2010
I've always understood that it was best practice to add event handlers in code in the page load event thus:
Button1.Attributes.Add("onclick", "alert('Hello');");
rather than "onclientclick=somefunction()"
My question is, how do you add event handlers to formview controls where the control(s) may only be on the edit template and not on the insert and read only templates.
Simply putting the code in the page load would produce an error.
Where should the statement be placed in such scenarios?
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Oct 25, 2010
My aspx has a placeholder I am dynamically loading a user control into the placeholder
like this:
Control dynamicControl = Placeholder1.Page.LoadControl("~/SiteUserControls/Message/MessageInbox.ascx");
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Jan 13, 2010
I'm developing an ASP.NET Web application with WebForms and C#.
I have this aspx page:
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<div id="divBody">
<div id="divHeader">
<asp:Button ID="Edit" runat="server" Text="Editar" onclick="Edit_Click" />
</div>
<div id="leftColumn">
<asp:UpdatePanel ID="UpdatePanelLeft" runat="server">
<ContentTemplate>
<asp:Label ID="TryText" runat="server"></asp:Label>
<asp:TreeView ID="DestinationTree" runat="server" ImageSet="Simple">
<ParentNodeStyle Font-Bold="False" />
<HoverNodeStyle Font-Underline="True" ForeColor="#5555DD" />
<SelectedNodeStyle Font-Underline="True" ForeColor="#5555DD"
HorizontalPadding="0px" VerticalPadding="0px" />
<Nodes>
<asp:TreeNode Text="Raiz" Value="Raiz">
<asp:TreeNode Text="Destino_1" Value="Destino_1">
<asp:TreeNode Text="Punto_1_1" Value="Punto_1_1">
<asp:TreeNode Text="Contenido_1_1_1" Value="Contenido_1_1_1"></asp:TreeNode>
<asp:TreeNode Text="Contenido_1_1_2" Value="Contenido_1_1_2"></asp:TreeNode>
</asp:TreeNode>
<asp:TreeNode Text="Punto_1_2" Value="Punto_1_2">
<asp:TreeNode Text="Contenido_1_2_1" Value="Contenido_1_2_1"></asp:TreeNode>
</asp:TreeNode>
</asp:TreeNode>
<asp:TreeNode Text="Destino_2" Value="Destino_2">
<asp:TreeNode Text="Punto_2_1" Value="Punto_2_1"></asp:TreeNode>
<asp:TreeNode Text="Punto_2_2" Value="Punto_2_2">
<asp:TreeNode Text="Contenido_2_2_1" Value="Contenido_2_2_1"></asp:TreeNode>
</asp:TreeNode>
</asp:TreeNode>
</asp:TreeNode>
</Nodes>
<NodeStyle Font-Names="Tahoma" Font-Size="10pt" ForeColor="Black"
HorizontalPadding="0px" NodeSpacing="0px" VerticalPadding="0px" />
</asp:TreeView>
</ContentTemplate>
</asp:UpdatePanel>
</div>
<div id="rightColumn">
<asp:UpdatePanel ID="UpdatePanelRight" runat="server">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Edit" EventName="Click" />
</Triggers>
</asp:UpdatePanel>
</div>
</div>
</form>
</body>
It is a header with two columns: On left column there is a TreeView, and on the left there is nothing (now there is a label to try the thing that I want to do).
When user select a node on treeview a click on Edit button. Code for click event is:
protected void Edit_Click(object sender, EventArgs e)
{
if ((DestinationTree.SelectedNode != null) &&
(DestinationTree.SelectedNode.Depth > 0))
{
BaseControl baseControl = new BaseControl();
UpdatePanelRight.ContentTemplateContainer.Controls.Clear();
switch (DestinationTree.SelectedNode.Depth)
{
case 1:
baseControl = (BaseControl)LoadControl("~/DynamicControls/Control1.ascx");
break;
case 2:
baseControl = (BaseControl)LoadControl("~/DynamicControls/Control2.ascx");
break;
case 3:
baseControl = (BaseControl)LoadControl("~/DynamicControls/Control3.ascx");
break;
}
UpdatePanelRight.ContentTemplateContainer.Controls.Add(baseControl);
}
}
Depending on node selected depth is going to load a custom control dynamically. It works, but when the user select another node on treeview, the original label is reloaded on right column.
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