We have created a UserControl. Inside user control we are creating an update panel. Inside the panel we are creating various controls such as TextBox, Button, DropDownList and ListBox and event associated with them buttonclick(),DropDown_selectedIndexChanged(),TextBox_TextChenged() etc. All the controls(including update panel) are created programatically using c#.
To ajaxify the events we have used ScriptManager.
ScriptManager is added on OnInit function programatically like as shown:
ScriptManager scriptManager = ScriptManager.GetCurrent(this.Page);
if (scriptManager == null)
{
scriptManager = new ScriptManager();
//scriptManager.EnablePartialRendering = true;
this.Controls.AddAt(0,scriptManager);
}
Every time after page load only one event get fired partial postback(which is desired) but after that no event gets fired .
All valid changes have already been done in web.config file for AJAX .
Please suggest the possible cause and solution of the problem.
On a partial postback, the ScriptManager will not be added because you are trying to add it outside the UpdatePanel (where it has to be). This works on the first page load because it's not a partial postback. But after the partial postback, the dynamically added ScriptManager won't be available to the page, and because you are trying to add it outside the UpdatePanel -- AddAt(0,...) - after a partial postback, it won't actually be added. On a partial postback you can only affect things inside the UpdatePanel that initiated the postback.
Bottom line is, you really can't add a ScriptManager dynamically, since it will never be there after a partial postback. Just like you can't dynamically add any other control outside of an UpdatePanel after an event sourced inside it.
Related
Allright so I have a slight issue when I want to load some basic usercontrols which contain an UpdatePanel inside to another page which is an usercontrol.
The set up:
Whenever an user clicks on a button a pop-up shows up containing some basic info on a certain person and a tab which contains the companies he worked for. The amount of companies he/she works for can range from 1 to 4~, so I do a query then for each company I get I add a view to a multiview, this view contains multiple simple user controls (Textfields inside an updatepanel). Now whenever I go to the page I get this error:
Cannot unregister UpdatePanel with ID 'UpdatePanel2' since it was not registered with the ScriptManager. This might occur if the UpdatePanel was removed from the control tree and later added again, which is not supported. Parameter name: updatePanel
Now I know this is a common error caused by generating UpdatePanels dynamically which aren't registered with the ScriptMaster. I can't add a PreInit event handler to the page which adds the UserControls with the UpdatePanels since it's an UserControl itself.
My question is:
How can I get rid of this nasty error in a not so nasty way e.g. not a hardcoded sub routine which adds the UpdatePanel to the scriptmaster
You could define the functionality you want to add inside your user controls. I have done the same in the past, adding the following, inside of my user control.
override protected void OnInit(EventArgs e) {
// your code here
}
Add a ScriptManager on your MasterPage before the UpdatePanel. And your updatePanel is a bit confusing so might change it as well. :)
Please I need someone to help me with this issue:
When I select an item from an .ascx usercontrol 'DropDownList Box' added to a master page with PlaceHolder1.Controls.Add(LoadControl("//UserControls/mycontrol.ascx"));
The .ascx user control disappears after the item has been selected
You don't show your code, so it's hard to provide an exact answer. but probably you add your user control dynamically only one time and it disappears after each postback.
You need to load Usercontrol after each postback so you need to load Usercontrol in something like Page_load method if you don't.
I dynamically load a User Control, with an Update Panel inside a Place Holder.
When I click a button from the User Control, should refresh the Update Panel contents, but it refresh the entire page instead, and the User Control is disappearing from the page, because the page's Page_Load does not load anything if it's a PostBack.
How I can fix it?
Whenever a partial or full postback happen , Automatically all update() method of all updatepanels fire . For preventing such this behavior you need to set UpdateMode="Conditional" property . In this situation you need to specify asynchronous trigger Or ChildrenAsTriggers=true .
for preventing a dynamically loaded-usercontrol to be disappear ,It's good to save it in ViewState , Here is a tutorial and sample application
I think you'll need to reinject the control in page_load or pre_render. Dynamically created controls don't live through postback.
Make sure you are creating the control EVERY page request, regardless of GET/POST. Also, make sure you are giving it the same ID.
I like to override the CreateChildControls method.
You need to add the control page to the page in the page_init method. It has to be added on each post back. The control will retain all the values even after adding it back.
There is a full working example at this link.
Assume I have an asp:GridView with some customer information. On that page I also have a button which allows me to add a new user to the GridView. When I add the click the user, I databind the gridview again in the button click. Correct me if I am wrong, but if the asp.net lifecycle or at least part of it is in the following order:
page_load
Hookup event handlers such as my button click
page_preRender
Does this mean that if I put the databinding for the gridview in preRender, that is the only place I need to worry about calling it. I can remove it from the button click. This is what I think, but I am not sure if my thinking is correct, so I would like some more insight as to the benefit of putting code in PreRender as opposed to PageLoad
By PreRender, you assume that most logic in the page that would affect the binding result has been completed (usually in Page_Load, but anywhere earlier really).
Controls in the .Net framework by default do their binding in the PreRender event (makes sense, bind to the datasource at the last possible moment...could be that you changed the data 400 times earlier in the lifecycle). Here's the full layout of the 2.0 lifecycle for reference.
PreRender - Before this event occurs:
The Page object calls EnsureChildControls for each control and for the page.
Each data bound control whose DataSourceID property is set calls its DataBind method. For more information, see Data Binding Events for Data-Bound Controls later in this topic.
The PreRender event occurs for each control on the page. Use the event to make final changes to the contents of the page or its controls.
I have an ASP.NET web form which I am adding a variable number User Controls to. I have two problems:
The User Controls are added to a PlaceHolder on the form in the first PageLoad event (I only add them when "(!this.IsPostback)", but then when the form is posted back, the controls are gone. Is this normal? Since other controls on the form keep their state, I would expect these dynamically added ones to stay on the form as well. Do I have to add them for every postback?
I also have a button and an event handler for the button click event, but this event handler is never called when I click on the button. Is there something special I have to do to catch events on dynamically added controls?
Yes, you need to add them in every postback.
Yes... the control needs to be in the control hierarchy before asp.net dispatches the event (i.e. create the dynamic controls as early in the page lifecycle as possible).
1) You should add the controls on the Pre-init (Page life cycle)
2) You have to attach the event handler to the event of the created button.(events might occur much later in the page life cycle than the same events for controls created declaratively)
To achieve this, add your controls at page init instead of page load. (re-add at postback)
You'll need to know the id of the buttons added to bind them to the event.
I ran into a similar problem. I had a page that displayed a collection of custom web controls. My solution was to add an additional invisible web control so that when I clicked a button to add another control that I would just use the invisible one. Then on post back my load function would add another invisible control to the collection.
I figured out yesterday that you can actually make your app work like normal by loading the control tree right after the loadviewstateevent is fired. if you override the loadviewstate event, call mybase.loadviewstate and then put your own code to regenerate the controls right after it, the values for those controls will be available on page load. In one of my apps I use a viewstate field to hold the ID or the array info that can be used to recreate those controls.
Protected Overrides Sub LoadViewState(ByVal savedState As Object)
MyBase.LoadViewState(savedState)
If IsPostBack Then
CreateMyControls()
End If
End Sub
I ran into the exact same problem and struggled through like 5-6 hours.
I'm posting this maybe someone like me could get help.
1) You should initialize your controls at Page.PreInit event. (In my case I had to add my controls to a place holder so I extended PreInit to load those controls before but you don't need to do that. It depends on your scenario.)
2) You should bind those exact methods to your controls after you initialize them in your Page.PreInit event.
Here is my sample code:
protected override void OnPreInit(EventArgs e)
{
// Loading controls...
this.PrepareChildControlsDuringPreInit();
// Getting ddl container from session and creating them...
if (GetDDLSession().Count != 0)
{
foreach (DropDownList ddl in GetDDLSession())
{
ddl.SelectedIndexChanged += SelectedIndexChanged;
phDropDowns.Controls.Add(ddl);
}
}
base.OnPreInit(e);
}
public static void PrepareChildControlsDuringPreInit(this Page page)
{
// Walk up the master page chain and tickle the getter on each one
MasterPage master = page.Master;
while (master != null) master = master.Master;
}