I have three usercontrols uc1.ascx ,uc2.ascx ,UC_Combined.ascx
UC1 has one label control
UC2 has one Dropdownlist Control
UC_Combined is created by combining UC1 and UC2
Now I placed UC_Combined.ascx on my aspx page webForm1.aspx has one more Label servercontrol
Now when I run my webForm1.aspx page I can see see DropDown list and a Label
Now when I select an Item from dropdown list ,I want the value of the selection to display to the Label
Can some one suggest me how can I do this .
It's not best to create a dependency between parent and child controls. Something you should generally avoid. But, if you have to do it or in some way makes your life alot easier then there are a few techniques for achieving this while keeping the controls somewhat decoupled. I would suggest you do the following:
Implement a PostBack handler that will store the value of the DropDownList in the "Items" collection of the HTTP Context (via HttpContext.Current.Items["ddlValue"] = val). The "Items" collection is a hashtable that has a lifespan of a single HTTP request. This means that it is cleared after the current HTTP request has been responded to. It's a nice lightweight means of transporting data between components.
Implement a property in UC1 that lazy loads the value from the "Items" collection and reference the property in your markup with the <%= %> syntax. Doing it this way ensures that you aren't trying to grab the value until Render (which is when the <%= %> code is executed), well after the PostBack handler event has been executed and the "Items" entry has been added. This way you can do everything within the same PostBack.
Think you got it?
Easy. Implement a event on the uc containing the drop down like:
public event EventHandler<DDSelectionChangedEventArgs> DDSelectionChanged;
public virtual void OnDDSelectionChanged(DDSelectionChangedEventArgs e)
{
if (DDSelectionChanged != null)
{
DDSelectionChanged(this, e);
}
}
The selection changed handler of the dd then have to call OnDDSelectionChanged.
Register a handler onto that event in your page (aspx). This handler should then call something like ChangeText(text) on the second uc with the textbox. And the textbox is been updated.
So the communication between the uc's is driven by events and the page has the resposibility to wire the events up. The uc's are completely independent.
Related
good sirs!
I've been messing around with the next scenario:
First, I have a webform structured as a WebForm containing a DevExpress ASPXPopUpControl and some other controls. Inside the PopUpControl there is a UserControl (lets call it ucA) containing some other controls and a UserControl (called ucB) that contains a cursed ASPxHtmlEditor (added because it's a new requirement).
When the user hits a button on main webform I show the PopUp (originally was a jQuery dialog but since HTMLEditor messes up with jQuery I've been forced to break the standard and use the popup) which contains the ucA. The user fills some fields in ucA and hit the save button. After user hits, I save some dataz and at this point I need to recover a textbox value placed in the webform.
I'm using Parent.FindControl["myTextBox"] but it considers the popupcontrol as parent. When I was using jQuery (before implementing the editor) it worked like a charm.
I feel it's something trivial but thrust me when I say that this stole many hours of research.
Thanks in advance.
EDIT I forgot to mention that I want to look for another UserControl at main webform. This uc its used to display core messages to the user so when he hits the save button, save happens, popup is closed and i look (Parent.FindControl("myUCMessageBoard")) from the ucA for the usercontrol to display a "Transaction complete" message.
I'm thinking you're going to have to do something a little hacky, by using ViewState. If I understand correctly, you are trying to get access to a TextBox's Text on the Web Form, from a UserControl nested within a PopupControl (so you can't traverse all the way up to Web Form Level).
So, what I'd do at some point in the process is store the text in a ViewState variable that you can access from the User Control. It's not optimal, but since you're already hacking to get it to work, what's a little more hacking?
You should expose all controls from ucA as properties, then look for the control inside the DevxPopup the same way you doing. Given that all the controls that you need at the ucA has properties to access them, you could do all the logic you need!
Example:
public ucA : UserControl
{
public string myTextBoxText
{
get
{
return ((TextBox)Controls.FindControl("myTextBox")).Text;
}
}
/*And lot of controls*/
}
Then you looking for the popup at the Form
var ucA = (UcA)Form.Controls.FindControl("myPopup").Controls.FindControl("myucA");
ucA.myTextBoxText = /*Do stuff here with the text*/
Hopes this help you!
There's loads of posts on this subject on the net, but I cant find one that fits my situation;
I've have a BasePage class, which my .aspx inherit from; I also have BaseLabel & BaseDDL classes, which extend Label & Dropdownlist respectively. On top of this I have a ReadyDDL class, which combines BaseLabel & BaseDDL into a single control (but this is a class, not a user control) and renders them with their own Div, Table, TableRow, TableCells, & another Label. The ReadyDDL class enables me to define label & dropdownlist & layout in a single html statement as per:
<moc:ReadyDDL ID="Person" runat="server" Member="#UserID" Caption="Create strike for"
DataSourceSQL="SELECT ID, UserName FROM [User] WHERE isDeleted = 0 AND ClientID = 3" TextField="UserName" ValueField="ID"
OnSelectedIndexChanged="ddl_SelectedIndexChanged" />
However I have a problem or two:
a) The event doesnt fire. The posts I have read on this subject say that the dropdown must be recreated OnInit & all will be fine. BUT -
I'm not dynamically creating a dropdownlist, but a custom extension of one - thus the code which creates the dropdownlist isnt in my aspx, where the event handler is defined, but is in a separate .cs file and accordingly, I cannot write
ddl.SelectedIndexChanged += new EventHandler(X);
because X doesnt exist in the class, only the page.
The only way I've found to get around this is to expose a string property (OnSelectedIndexChanged) which sets another property in BaseDDL, and when BaseDDL is rendered, to add the OnSelectedIndexChanged property to the markup produced.
The html produced looks ok, and on screen it looks ok, and it does postback when I change the selection in the control, but the eventhandler doesnt fire: it currently just contains a couple of assignment statements, which I have a breakpoint on, and which isnt reached.
On reflection, I suppose, rendering the handler only adds the event to the control in so far as the client is concerned, and the server doesnt know about it - but how can I overcome this, and define the handler at control initialisation, when the handler isnt in the same source code file as the initialisation code?
Does anyone have any ideas on either (1) getting the event to fire, or (2) how I can define the event in code, rather than via rendering?
Any questions please ask. Any help or suggestions will be appreciated, and I will mark Q as answered if suitable information comes.
b) the selected value is lost on postback. I know I have to do something with Viewstate, but I havent figured out just what, yet. If you know how I can implement a solution to this, a short example would be much appreciated.
Appears that your are developing a composite control - the correct way to go about this is to inherit from CompositeControl class and override CreateChildControls to add your child controls. This method is called by ASP.NET early in life-cycle and that would eliminate your view-state related issues.
See this article for developing composite control. For event, string typed property is not going to work - you must define the event at your composite control level. You can bubble up the child's event by raising your own event in the handler (this is shown in the article). Another way would be short-circuit the event handlers. For example, define the event in your composite control such as
public event EventHandler SelectedIndexChanged
{
add
{
childDdl.SelectedIndexChanged += value;
}
remove
{
childDdl.SelectedIndexChanged -= value;
}
}
childDll is reference to your child ddl control.
I have a page with multiple update panels, each containing dynamically created User Controls that contain a button control.
When The button in a control is clicked the control no longer exists in the page load event and so the click event of the button within the control cannot be raised.
To get round this I am currently recreating ALL the controls on the page in each page load event, but this is obviously causing a lot of unneccesary page updating. In any given partial postback, the only control(s) that need to be recreated are the ones in the update panel containing the control that has been clicked.
How then can I best identify which control has been clicked in page_load and then only recreate the controls in the relevant update panel to be able top then access the click event of that control?
I know I can do the following
if (ScriptManager1.IsInAsyncPostBack)
{
string clickedControlId = ScriptManager1.AsyncPostBackSourceElementID
}
But this isnt hugely useful as knowing the ID of the control doesnt neccesarily help me identify which Update Panel it belonged to. Is there a way of adding a command argument to the control when it is created at run time and reading that command argument in the page load event during the partial postback?
If not, any other suggestions?
Many thanks
Stewart
1) Stop using update panels they add an unnecessary level of complexity that creates more problems than is worth, especially when you have more than one in a page.
2) Stay away from mixing Ajax functionality with server-side logic. You will end up writing a lot of code to compensate one or the other.
What I suggest:
Don’t use update panels!
Keep the code that generates the initial page load. Instead of posting to the server with a .Net button, use a regular button and use the onClick=”foobar_ajax(id, ….Update UI)” to make an ajax call to update the data on the server. Include the ID of the item(the control) you are clicking on. When your ajax call is done you may not need to do anything or you could update the UI with some new data from the server (I recommend refreshing after saving).
Read: Calling the page method with jQuery instead.
http://encosia.com/using-jquery-to-directly-call-aspnet-ajax-page-methods/
I'm working on an ASP.NET project in which the vast majority of the forms are generated dynamically at run time (form definitions are stored in a DB for customizability). Therefore, I have to dynamically create and add my controls to the Page every time OnLoad fires, regardless of IsPostBack. This has been working just fine and .NET takes care of managing ViewState for these controls.
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
RenderDynamicControls()
}
private void RenderDynamicControls()
{
//1. call service layer to retrieve form definition
//2. create and add controls to page container
}
I have a new requirement in which if a user clicks on a given button (this button is created at design time) the page should be re-rendered in a slightly different way. So in addition to the code that executes in OnLoad (i.e. RenderDynamicControls()), I have this code:
protected void MyButton_Click(object sender, EventArgs e)
{
RenderDynamicControlsALittleDifferently()
}
private void RenderDynamicControlsALittleDifferently()
{
//1. clear all controls from the page container added in RenderDynamicControls()
//2. call service layer to retrieve form definition
//3. create and add controls to page container
}
My question is, is this really the only way to accomplish what I'm after? It seems beyond hacky to effectively render the form twice simply to respond to a button click. I gather from my research that this is simply how the page-lifecycle works in ASP.NET: Namely, that OnLoad must fire on every Postback before child events are invoked. Still, it's worthwhile to check with the SO community before having to drink the kool-aid.
On a related note, once I get this feature completed, I'm planning on throwing an UpdatePanel on the page to perform the page updates via Ajax. Any code/advice that make that transition easier would be much appreciated.
From Dirk to Dirk :-)
What do you mean with RenderDynamicControls? Create and set controls? If this is your intention not ASP.NET is managing your ViewState, but you do. If you fill the controls on every load, you always overwrite the existing ViewState!
If you want to use the ViewState, create your controls in the pages init event and fill them in the load event, but only if the request isn’t a postback. This is necessary, because ASP.NET recreates the ViewState between init and load. And this is also the reason for the two “rendering cycles” you describe. You need the first control creation cycle because ASP.NET can’t restore the ViewState without a proper control set and ASP.NET can’t react proper on your response without it.
Back to your code: In general your RenderDynamicControlsALittleDifferently wouldn’t work - because you create your controls too late in the pages life cycle and you would damage the ViewState by inserting new objects to the control collection. In a similar situation I solved this problem by a redirecting the page to itself (Response.Redirect). In this case RenderDynamicControls would do the job, based on a “little differently situation” after you change your internal state.
Problem with dynamic controls
Hello all,
I'm wanting to create some dynamic controls, and have them persist their viewstate across page loads. Easy enough, right? All I have to do is re-create the controls upon each page load, using the same IDs. HOWEVER, here's the catch - in my PreRender event, I'm wanting to clear the controls collection, and then recreate the dynamic controls with new values. The reasons for this are complicated, and it would probably take me about a page or so to explain why I want to do it. So, in the interests of brevity, let's just assume that I absolutely must do this, and that there's no other way.
The problem comes in after I re-create the controls in my PreRender event. The re-created controls never bind to the viewstate, and their values do not persist across page loads. I don't understand why this happens. I'm already re-creating the controls in my OnLoad event. When I do this, the newly created controls bind to the ViewState just fine, provided that I use the same IDs every time. However, when I try to do the same thing in the PreRender event, it fails.
In any case, here is my example code :
namespace TestFramework.WebControls
{
public class ValueLinkButton : LinkButton
{
public string Value
{
get
{
return (string)ViewState[ID + "vlbValue"];
}
set
{
ViewState[ID + "vlbValue"] = value;
}
}
}
public class TestControl : WebControl
{
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
Controls.Clear();
ValueLinkButton tempLink = null;
tempLink = new ValueLinkButton();
tempLink.ID = "valueLinkButton";
tempLink.Click += new EventHandler(Value_Click);
if (!Page.IsPostBack)
{
tempLink.Value = "old value";
}
Controls.Add(tempLink);
}
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
ValueLinkButton tempLink = ((ValueLinkButton)FindControl("valueLinkButton")); //[CASE 1]
//ValueLinkButton tempLink = new ValueLinkButton(); [CASE 2]
tempLink.ID = "valueLinkButton";
tempLink.Value = "new value";
tempLink.Text = "Click";
Controls.Clear();
Controls.Add(tempLink);
}
void Value_Click(object sender, EventArgs e)
{
Page.Response.Write("[" + ((ValueLinkButton)sender).Value + "]");
}
}
}
So, let's examine case 1, where the line next to [CASE 1] is not commented out, but the line next to [CASE 2] is commented out. Here, everything works just fine. When I put this control on a page and load the page, I see a link that says "Click". When I click the link, the page outputs the text "[new value]", and on the next line, we see the familiar "Click" link. Every subesquent time I click on the "Click" link, we see the same thing. So far, so good.
But now let's examine case 2, where the line next to [CASE 1] is commented out, but the line next to [CASE 2] is not commented out. Here we run into problems. When we load the page, we see the "Click" link. However, when I click on the link, the page outputs the text "[]" instead of "[new value]". The click event is firing normally. However, the "new value" text that I assigned to the Value attribute of the control does not get persisted. Once again, this is a bit of a mystery to me. How come, when I recreate the control in OnLoad, everything's fine and dandy, but when I recreate the control in PreRender, the value doesn't get persisted?
I feel like there simply has to be a way to do this. When I re-create the control in PreRender, is there some way to bind the newly created control to the ViewState?
I've struggled with this for days. Any help that you can give me will be appreciated.
Thanks.
ViewState-backed properties are only persisted to ViewState if the control is currently tracking ViewState. This is by design to keep ViewState as small as possible: it should only contain data that is truly dynamic. The upshot of this is that:
ViewState propeties set during the Init event are not backed to ViewState (because the Page has not yet started tracking ViewState). Thus Init is a good place to add controls and set (a) properties that won't change between postbacks (ID, CssClass...) as well as initial values for dynamic properties (which can then be modified by code in the rest of the page lifecycle - Load, event handlers, PreRender).
When dynamically adding controls in Load or PreRender, ViewState is being tracked. The developer can then control which propeties are persisted for dynamically added controls as follows:
Properties set before the control is added to the page's control tree are not persisted to ViewState. You typically set properties that are not dynamic (ID etc) before adding a control to the control tree.
Properties set after the control is added to the page's control tree are persisted to ViewState (ViewState tracking is enabled from before the Load Event to after the PreRender event).
In your case, your PreRender handler is setting properties before adding the control to the page's control tree. To get the result you want, set dynamic properties after adding the control to the control tree:
.
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
ValueLinkButton tempLink = new ValueLinkButton(); // [CASE 2]
tempLink.ID = "valueLinkButton"; // Not persisted to ViewState
Controls.Clear();
Controls.Add(tempLink);
tempLink.Value = "new value"; // Persisted to ViewState
tempLink.Text = "Click"; // Persisted to ViewState
}
As others have statement you'll need to ensure that you are creating via the Init method. To learn more about the ASP.NET page life cycle check out this article: http://msdn.microsoft.com/en-us/library/ms178472.aspx
I'm already re-creating the controls in my OnLoad event.
That's your problem. OnLoad is too late. Use Init instead.
Thank you for your help, but I tried that and it didn't make a difference. Besides, OnLoad works just as well for dynamic controls as OnInit, as long as you give your controls the same IDs every time.
I believe that once you have added the dynamic controls to the page in PageLoad, the ViewState is bound to the controls and the "ViewState still needs to be bound" flag (in concept, not an actual flag) is cleared. Then, when you recreate the controls, the existing ViewState is no longer bound.
I faced something similar last year, only in my case I did not want the ViewState to rebind. My issue is that I was not recreating the previous controls, which is why I think that the pseudo-flag notion above applies.
Try calling Page.RegisterRequiresControlState(). You can also use RequiresControlState() to check if it's already been registered.
ViewState works on the Page and its child objects. The new control in [Case 2] has not been added to the Page (or any of its children). In fact, in case of the code above, the object will be out of scope as soon as the OnPreRender method ends and will be garbage collected.
If you absolutely have to swap out the control, you will need to remove the old control from its parent using Remove() method and add the new control at the right place using AddAt().
If the control was the only child of the parent, the code would be something like the following.
ValueLinkButton tempLink = new ValueLinkButton();
Control parent = FindControl("valueLinkButton").Parent;
parent.Remove(FindControl("valueLinkButton"));
parent.AddAt(0, tempLink);
Control added before SaveViewState method called in control life cycle should persist their values. I would concur with Joe's answer. Check this image
http://emanish.googlepages.com/Asp.Net2.0Lifecycle.PNG
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