Usercontrols - Wiring Events On Dynamically-loaded User Controls?
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.
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); } }
I have written a user control that captures some user input and has a Save button to save it to the DB. I use a repeater to render a number of these controls on the page - imagine a list of multiple choice questions with a Save button by each question.
I am loading the user control inside the repeater's ItemDataBound event like this (code simplified):
[code]....
The problem is that when the Save button is clicked, the page posts back, but lbnUpdate_Click is not called. The Page_Load event of the page itself is called however.
I should mention that the repeater is part of a user control, and that user control is loaded inside another user control (this is a DotNetNuke site which makes heavy use of user controls). The Save button link looks like this:
I'm doing a menu that loads levels dynamicly, when you click on a item the next level is loaded asynchronously. For each menu item I have a user control. Every user control is declared in its parent, for example, the "secondlevelcontrol" has the reference to "thirdlevelcontrol".With this level of nesting, I want to manage the asynchronous calls on every user control so, when the first level is loaded the javascript to load the second is loaded too. When the second level is loaded the javascript to load the third is loaded too.
To do asynchronous calls I'm implementing ICallbackEventHandler interface. As you can see in the examples, controls are added to the page as plain html. The method "ProcessOnLoadEvent" executes all lines of the "OnLoad" event of the user control.An example of the implementation is this for the user control of fourth level:
public string GetCallbackResult() { return _callbackRendering; }
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 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.
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:
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.
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?
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.
We have an application where the controls are dynamically added to the form based on the logged in user,
This user controls related data is stored in the database. There is lot of logic in the code behind in the asp.net webforms which is so messy to maintain it, we are planning to re-write it using the MVC framework.
I would say there would be rougly 50 different forms based on the user logged in, is it good idea to create so many views and redirect to the appropriate view based on the logged in user, in some of the forms there might be minor difference like the order of the Control might change.
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.
I am trying figure out how I handle events in a dynamically added user control. Basically I can add user controls dynamically to my form (I am then storing them in an ArrayList in a Session variable that I use to reload them on my Page_Load). Each control has a button on it. However, whenever I click the button, the event never fires (code is never reached). I assume it has something to do with the control being dynamic, and when I click a button, it goes out of scope, and when I reload it something is lose in the event handling.
Here's my code for adding a user control:
Code: Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load Dim alContact As New ArrayList If Not IsPostBack Then ' Dummy controls for testing Dim oContact As New ASP.ContactControl
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.
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?
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); }
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.
I'm using a FormView with a dynamically loaded item template. Inside the template (an ascx file loaded through Page.LoadTemplate(...) ) there is a button and I need to invoke the click event on that button.
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.
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().
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:
I'm trying to make web form with two placeholders. Firs holder contains user control witch has list of buttons, each button opens different user control to second placeholder.
I get it to show user control in second placeholder but i can't get dynamically created user controls to fire events.
So how i can dynamically create working user control with button click?
Here is how i create those controls:
[Code]....
"field" is hidden field containing filename of user control to be created.
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:
I have the usual problem of dynamically created usercontrols not hitting the event handler for a linkbutton inside the control, but I've checked the usual problems and I can't work out what's wrong. I'm calling a function to create the controls at the bottom of my page.load (although I did try page.init as well just in case) outside of my page.ispostback check, and I'm setting the controls id's to a fixed name which is consistent across postbacks. Any ideas what's wrong?
[Code]....
Usercontrol code:
<asp:LinkButton runat="server" ID="lnkDeleteGroup" Text="Delete this group" />
