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. :)
Related
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.
I've been getting this exception in my code and wondered if anyone could help me out.
I have a Repeater Control bound to an ObjectDataSource, and the itemtemplate for the repeater contains a User Control (ASCX). This user control in turn contains several other controls, mainly a GridView that is associated with an ObjectDataSource.
On initial use of the controls in this setup, everything works great - data displays properly. However, when I change a filter option (dropdowns outside of the repeater), and then rebind the Repeater, I get the exception:
The ObjectDataSource control 'expDataSource' does not have a naming container. Ensure that the control is added to the page before calling DataBind."
at System.Web.UI.WebControls.DataBoundControlHelper.FindControl(Control control, String controlID)
...
...
at System.Web.UI.WebControls.ObjectDataSource.LoadCompleteEventHandler(Object sender, EventArgs e)
I'm not sure what the problem is - I've read in a few places that moving the datasource outside of the ASCX control might help - this does nothing. The objectdatasource appears to be properly structured, and as I said, it works the first time (only).
I noticed in the stack trace for the exception that this is occurring when ASP.NET is calling FindControl() after LoadComplete() occurs. If I step through my code, it appears as though all my code is finished executing before this happens, so it's all "system" code.
Why would ASP.NET not be able to find this datasource control in the LoadComplete Handler?
Thanks!
Other Notes:
This error occurs every other time. So the first time the data loads properly, then on second refresh fails with this error. Clicking "Load" again, it works (on the third time).
On the times that it fails, it looks like "Page_Load" is being called twice in the ASCX control. So the patterns are:
Working Pattern:
Page_Load on Parent Page
Page_Load on ASCX
Data Loads fine
Failing Pattern:
Page_Load on Parent Page
Page_Load on ASCX
Page_Load on ASCX
Exception
This is all happening from a call to "Repeater.DataBind()", but it behaves differently depending on if it has already been bound or not (evidently).
More Notes:
Real strange behavior. I removed the list of SelectParameters from the bottom of the ObjectDataSource, and all of a sudden, the page does not reject the ObjectDataSource as not having a NamingContainer. Of course, without these parameters, Databinding won't actually work...I can add them in the code, but why would it matter?
Found a strange solution, that I'll post and we can discuss to maybe figure out why this fixed it.
On my page, I had the following structure (paraphrasing the tags somewhat):
Page
DropDownFilter
Repeater
UserControl X
ObjectDataSource
ControlParameters Referencing DropDownFilter
End ObjectDataSource
End UserControl X
End Repeater
End Page
So as you can see, within the Repeater ItemTemplate was the user control, which in turn had the "guilty" ObjectDataSource with ControlParameters. These control parameters had the name of the DropDownList filter on the parent page referenced (so basically, if this control was added to any other page, it would of course fail if it couldn't find a control with the proper name).
So when I went through and changed all the ControlParameters to Parameters (removed the reference to that DropDownList control), now I no longer get the error.
All I can assume is that the fact that this datasource referenced a control on the parent page meant that it was having trouble getting added back to the page's control set on a DataBind(). You would have thought it would fail the first time if it was going to fail at all, so that's still a mystery.
Any thoughts?
This is an exceptional error in ASP.NET DataControls. I had similar problem and lost few months behind this eccentric error, but finally got the solution. The reason is; To display items in ItemTemplate, we should use a server control in the LayoutTemplate to act as the placeholder for the ItemTemplate. For example, we could use a Table/Div control with an ID Property in Layout Template. At run time, this placeholder control will be replaced with the contents of the ItemTemplate and "naming container error" will be disappeared.
Finally, if you are having an objectDataSource in ItemTemplate, make sure that you added somthing(like table/Div) with "Id" property in Layout Template.
Thanks,
Sunil.
Ray hit the nail on the head. You are definitely missing an "if(!IsPostBack)" somewhere. How are you adding the user control to the repeater? Is it dynamic? You say it's in the ItemTemplate, so probably not... But multiple calls to Page_Load imply multiple copies of the control.
Use both DataBind. Example:
SqlDataSource1.DataBind();
ListView1.DataBind();
I have a checkboxlist and textbox controls on my asp.net page and the are dynamically created and added to the page. When I populate the values and submit the form, the values are empty by the time it hits the server. Any help?
They are empty because they are being re-created too late in the page lifecycle.
Without knowing the precise point in the ASP.NET Page Lifecycle you're adding your controls, (though I'd guess it's either Page_Load or an event handler), it goes something like this:
Build control tree
Add dynamic controls
Render
(Postback)
Build control tree
Reconstitute viewstate & bind to Post values
Add dynamic controls
Render
To solve this, you need to make sure your controls are created early enough in the lifecycle. Standard practice is to break the "control creation" into a separate method, and during CreateChildControls, check to see if they need to be created:
override CreateChildControls()
{
if(IsPostBack)
{
EnsureDynamicControlsAreAdded();
}
}
This way, if they do need to be initially added by something as far late in the lifecycle as an event handler (Button_Click, for example), you can call the same EnsureDynamicControlsAreAdded method from there as well, and on the next round-trip they'll be created much earlier.
Further to Rex M's answer, you could try creating the controls in the "Page_Init" event - this is one of the first events in the page lifecycle, and is where I would normally create controls in a viewstateless page (NB: If you do this, do not surround the content of the Page_Init handler with an "if (!IsPostback)" - this will prevent it from working as intended).
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;
}
I am adding some user controls dynamically to a PlaceHolder server control. My user control consists of some labels and some textbox controls.
When I submit the form and try to view the contents of the textboxes (within each user control) on the server, they are empty.
When the postback completes, the textboxes have the data that I entered prior to postback. This tells me that the text in the boxes are being retained through ViewState. I just don't know why I can't find them when I'm debugging.
Can someone please tell me why I would not be seeing the data the user entered on the server?
Thanks for any help.
This is based on .NET v1 event sequence, but it should give you the idea:
Initialize (Init event)
Begin Tracking View State (checks if postback)
Load View State (if postback)
Load Postback Data (if postback)
Load (Load event)
Raise Changed Events (if postback)
Raise Postback Events (if postback)
PreRender (PreRender event)
Save View State
Render
Unload (Unload event)
Dispose
As you can see, the loading of ViewState data back to the controls happen before the Load event. So in order for your dynamically-added controls to "retain" those values, they have to be present for the ASP.NET page to reload the values in the first place. You would have to re-create those controls at the Init stage, before Load View State occurs.
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 believe you'll need to add the UserControl to the PlaceHolder during the Init phase of the page life cycle, in order to get the ViewState to be filled in by the Load phase to read those values. Is this the order in which you're loading those?
Ensure you are defining your dynamic controls at the class level and adding them to the ASP container:
Private dynControl As ASP.MyNamespace_MyControl_ascx
And when you instantiate the control, ensure you call LoadControl so the object is added properly:
dynControl = CType(LoadControl("~/MyNamespace/MyControl/MyControl.ascx"), ASP.MyNamespace_MyControl_ascx)
You have to create your controls in the Page_PreInit event handler. The ASP.NET server control model is tricky; you have to fully understand the page lifecycle to do it right.
As others have said, any form of control manipulation must be done before viewstate is created.
Here is a good link on the page lifecycle to help you out:
http://msdn.microsoft.com/en-us/library/ms178472.aspx
We have experienced the same thing and have handled it by using ghost controls on page_load that have the exact same .ID and then the post back picks up the events and the data. As others said it's the dynamic adding of the control after the init stages that the state is built already and controls added after aren't stored.
Hope this helps a bit.
I also want to add that I've seen user controls work the way that you'd expect them to just by setting the Control.ID property at run time. If you do not set the ID, items may get built in a different order and work oddly.