Finding Webpage Lifecycle In The ViewState Collection
Feb 8, 2011
When exactly is the view state accessible from the .Viewstate property of a control? From my observations, the closest event is on the Page.PreLoad event (at Page.InitComplete, Viewstate is still unavailable).
However, for controls that implement the IPostBackEventHandler interface the LoadValue() method is called and the .Viewstate collection is available (this occurs after Page.InitComplete and before Page.PreLoad).
Does anyone know of any additional events that can be used to know when Viewstate is available? Or any tricks (not excluding reflection on private/protected/internal members) that can be used to know if the Viewstate has loaded or not?
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Nov 8, 2010
In building custom controls, I've seen two patterns for using the viewstate. One is to use properties to disguise the viewstate access as persistent data.
public bool AllowStuff
{
get
{
return (ViewState[constKeyAllowStuff] != null) ?
(bool)ViewState[constKeyAllowStuff] : false;
}
set { ViewState[constKeyAllowStuff] = value; }
}
The other is to use private member fields and to override the Load/SaveViewState methods on the control and handle it all explicitly:
protected override object SaveViewState()
{
object[] myViewState = new object[2];
myViewState[0] = base.SaveViewState();
myViewState[1] = _allowStuff;
return myViewState;
}
protected override void LoadViewState(object savedState)
{
object[] stateArray = (object[])savedState;
base.LoadViewState(stateArray[0]);
_allowStuff = (bool)stateArray[1];
}
(I cut out a lot of safety checking for clarity, so just ignore that.) Is there are particular advantage to one method over the other? I can't see how they'd differ much performance wise. Version 1 is lazy, so I guess you save a bit if you don't need that particular value during a pass. Version 1 is also more abstract, hides the details better. Version 2 is clearer about when the data is actually valid and ok to read or modify (between the load and save) because it more clearly works within the ASP.NET lifecycle. Version 2 does tend to require more boilerplate code though (a property, a backing private field, and viewstate handling in two places) as opposed to Version 1 which combines all that into one place.
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Aug 5, 2010
I have an ajax form that has a simple click event. Inside the click event, at the end of the method, I have a Response.Redirect back to the same page. For the purpose of this thread, I will leave out the reasoning of this (it is just something that I had to do). Once the ajax call is complete and the redirect takes place, all of my default control viewstates get wiped out. The thing that doesn't make sense, is that if I define my own ViewState right before the Response.Redirect, these ViewStates also get wipedout. So, my question is, do ViewStates only hold their values after one postback/refresh? And, is there a way to use ViewState with the method described above? I am being forced to use the querystring to pass parameters.
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Mar 1, 2010
the exact difference between PreInit and Init in the ASP.NET Page LifeCycle ?
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Nov 9, 2010
According to the msdn documentation, as you can see on the diagram, a server control's "Data binding events" occurs after all "control changed events". So in the case of a DetailsView control, the ItemInserted event would happen before the database operation?
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Feb 17, 2010
when does the constructor on a page in asp.net page lifecycle get called?
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Apr 28, 2010
Maybe it's been a long day but I'm having trouble persisting a collection backed by the ASP.NET ViewState in a CompositeControl. Here's a simplified version:
public class MyControl : CompositeControl
{
public Collection<MyObject> MyObjectCollection
{
get {
return (Collection<MyObject>)ViewState["coll"] == null ?
new Collection<MyObject>()
: (Collection<MyObject>)ViewState["coll"];
}
set { ViewState["coll"] = value; }
}
}
public partial class TestPage : System.Web.UI.Page
{
protected void btn_Click(object sender, EventArgs e)
{
myControl1.MyObjectCollection.Add(new MyObject());
}
}
When the button is clicked, the event hander btn_Click executes fine, but the setter for MyObjectCollection never gets called, hence the new MyObject() never gets persisted.
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Jan 26, 2011
i am adding dynamic control (textbox) and i set the property to visible = false but i dont find the control in the tree collection, i want to hide it from user seeing it and read the value.
protected void gv_RowCreated(object sender, GridViewRowEventArgs e)
{
Students org = (namespace.Students )(e.Row.DataItem);
foreach (Registration reg in org.Registrations)
{
int _count = org.Registrations.Count;
for (int rowId = 0; rowId < _count; rowId++)
{
TextBox txtBox = new TextBox();
txtBox.ID = "_registration" + e.Row.RowIndex + "_" + rowId;
txtBox.Text = reg.Name;
txtBox.Visible = true;
e.Row.Cells[7].Controls.Add(txtBox);
}
}
}
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Aug 6, 2010
I'm new to LINQ and EF and I seem to be having trouble working this out.
I have a many-to-many relationship between my Location and Region tables. When adding or editing a Location, my interface allows the user to check any number of related Regions. If they click OK, I need to add any new relationships that were checked, and delete any existing relationships that have been unchecked. My basic code is shown below.
However, this code doesn't work. Lower down, the line location.Regions.Contains(region) returns false even when the location already is related to the region. The issue appears to be because the region is from my populated listbox that was initialized earlier and is no longer part of the current EF context. But if I try and add it, I get an error that there is already a Region with that ID.
It seems like what I want to do is change this line to something like location.Regions.Contains((r) => r.RgnID == region.RgnID) so I'm only testing for a particular ID. But this gives me the error "Cannot convert lambda expression to type 'TrailCalendar.Region' because it is not a delegate type."
I don't understand this error but, either way, I'm not sure how I can test if the relationship already exists without reloading a bunch of data, which I'd like to avoid.
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Feb 25, 2011
I have an ASCX control which is a special dropdownlist. I add that control dynamically to the page and fill it with data. This control has a postback that will change the contents of a second dynamically created standard dropdownlist.
When I change the selection on the first dropdown, the indexchanged fires and I get new data and attempt to place it in the second dropdownlist's items collection, by first clearing it then filling it with new data.
This works fine the first time a change the selection, but when I select a second time the following error is thrown:
The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request.
I'm not adding or removing new controls in the fired event, only changing data. And again, it works the first time, but doesn't subsequent times.
If I disable stateview on the child control, then the control just doesn't get updated with data at all.
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Feb 5, 2011
In my Global.asax file on Application_Start I create a certain number of routes in RouteTable.Routes by looping through a list of web pages collected from a database. This works fine, all routes are created and function as required. But in my web application the user can modify the database and therefore the collection of web pages. This means that during the life cycle of the application some of the routes become invalid, and new routes should be added.
What I wish to do is: The moment the user changes something to the web pages collection, I would like to clear the RouteTable and reload it by looping through the (modified) web pages collection again.
Unfortunately the Application_Start in Global.asax is ran only once, namely at the beginning of the application. I tried moving it to Session_Start which results in undesired behaviour due to the RoutesTable being static.
How do I give my user the ability to change the web page collection on-the-fly whilst having the static RouteTable remain 'in-sync' with it?
Edit
At the moment I do something like this (pseudo-code):
[code]....
The problem is that during the life cycle of the application users can add/modify/delete records in the webPageInfos, how do I update the RouteTable with these changes?
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Apr 20, 2010
I've ported a page from classic ASP to ASP.net. Part of what happens in this page is that a collection of custom types is generated and then displayed via Response.Write() commands. I'd like to get the business logic separated out into a code behind file (and maybe move this all into a user control), but I can't seem to figure out how I'd actually display the collection once it's been generated. I want to specify a master page here, too, so the code can't stay inline. Here's a very stripped down version of the current code:
[code]....
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May 21, 2010
in a web page i can fill a form and after submit a was redirected to a confirmation page and there, i must confim and then it's submited.
i'm creating a bot for filling the form but i idn't know how to do it in just one step. this means to send information and confirm withoud waiting for loading confirmation form and then confirm that.
is it possible?
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Apr 28, 2010
I deploy a simple web app,that works fine on my local system, on a remote server. The webform consist of a Menu control and a Listview control. If I browse the page and then leave it for like 20 minutes untouched and then try to select an entry from the menu I am getting the following error -
Webpage error details
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; InfoPath.1; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; AskTB5.6)
Timestamp: Wed, 28 Apr 2010 07:39:24 UTC
Message: Sys.WebForms.PageRequestManagerServerErrorException: An unknown error occurred while processing the request on the server. The status code returned from the server was: 500
Line: 4723
Char: 21
Code: 0
URI: http://www.shoeslocation.com/ScriptResource.axd?d=w3IpLZb6A3e5QHkk7kOTg4vdE8qw_8oIJ-6Kv5NpYYlCqyodfByoMbMvCI7RsUpH3U_p3tMqnuLd_nCq_qPaX4weg2w6s1FlfA_eQbVY-nU1&t=55414254
Before that I used to get the following error -
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.So I added the following to the Pages tag in the web.config validateRequest="false" enableEventValidation="false" viewStateEncryptionMode ="Never"
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Aug 24, 2010
I'm trying to write a bit of code that will format all the numeric values in lables in my gridview. here's what i am doing right now:On the RowDataBound Event, i create a row object for the row that is currently being bound.then i go use the FindControl method to grab each label by name.Problem is there's too many columns in this table and i really dont wnat to have to type it all out. Here's an example of what i am currently doing
[Code]....
Can i use myRow.Controls to grab a list of all the controls and then somehow get a list of all labels in the collection and then use a for loop to go through and format each label?
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Jul 26, 2010
I have a list of objects that I want to bind to a gridview. Creating that list and binding it works fine for most of the public properties in that list.
There are some objects contained in each of those objects... for instance there is an Address object.
object.Address.Line1;
object.Address.Line2;
When I bind this to my gridview, I have no issues with stuff like object.DateRegistered, but how can I access things like object.Address.WhatEverProperty? I always get this error:
"A field or property with the name 'xxx.xxxx' was not found on the selected data source."
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Mar 31, 2010
I want to know that how i use the collection class for storing some data and save it letter in the data base.
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Oct 9, 2010
Now here is the weird thing. First i am running it locally on the built in vs2008 web server.I load my control in fine, do a postback from a linkbutton, locally on my machine it all works fine, no issue.However when it goes onto my host, it falls over with the message:
Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request.Now i also load controls dynamically and use postbacks and things in the admin area of the site...and that works fine, however my front end just keeps failing? See the code behing below:
[Code]....
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Jan 11, 2011
I have problem getting values from viewstate in GetTopThemes.
<asp:ObjectDataSource
ID="sourceGetTopThemes"
runat="server"
TypeName="DBConnection"
SelectMethod="GetTopThemes"
EnableViewState="true"></asp:ObjectDataSource>
[Code]....
}
[Code]....
when the page is not Posted back, I saved all values in the viewstate.
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Mar 25, 2011
I have an ASP.NET app with lots of textboxes all over the page that need updating at various points through program execution.
These textboxes actually belong to a certain class, so for easy updating I thought I could create a Dictionary(Of string, object) and add the control.ID and the control to it and then for updating do something like this:
(in case of updating textbox.text):
[code]....
However the text property of the textbox does not actually get updated. I'm mainly trying to avoid having to manually do textbox.text = somestring for each one of my textboxes every time I have to update them.
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Apr 30, 2010
I have been getting this error a lot lately with some of my users, and I had a couple of concerns with view state and I have read so many articles but I am still lost..
1. I use masterpage on all the pages and I need viewstate for some of the pages but..
There is a page where a user will fill out the information and then submit this data to a cgi server, and it is where I get most of the Client Disconnected errors, what would happen if I disable viewstate when they click on that button?
Now when a user browses from one page to another, does the view state from the previous page get deleted? If not how would I delete it?
Does the master page have its own viewstate? Would I be able to make sure none of items on my master page are using the viewstate?
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Sep 24, 2010
I have a shopping cart page (Cart.aspx) that has a button that will (sometimes) post to a third party payment gateway, if payment is necessary. The payment gateway will process the payment and then do a silent post to my website (Order.aspx) so I can update the order status.
Order.aspx always throws an invalid viewstate error, even though viewstate is disabled on the page.
What's happening is that Cart.aspx (which has viewstate enabled) posts to the payment gateway, and the gateway will post it back as part of the silent post. Even though Order.aspx has viewstate disabled and validation disabled, it still tries to validate the __viewstate field it's being given.
I know setting EnableViewState=false will disable the rendering of the __viewstate field, but if another page provides the field, shouldn't it still skip validation? I tried calling ViewState.Clear() on the Page_Init event of Order.aspx, but ViewState is apparently empty. how to get around this? I don't want to disable ViewState on Cart.aspx (in some cases it may be necessary), but I can't figure out how to clear it on Order.aspx.
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Dec 16, 2010
I'm using a file manager-type WebControl that does lots of postbacks. It's placed inside a Page that is relatively complex. I would like to prevent the WebControl from causing the whole Page to go through the lifecycle.
Is there any way to isolate the WebControl from the rest of the Page? The only way I can think of is sticking the WebControl in a separate Page and creating an iframe in the original Page. Unfortunately that also means my WebControl properties/settings are no longer in the original Page. If I want two instances of the WebControl with different settings, then I have to create a Page for each setting and reference the correct one in my iframes. Not quite as "drag & drop" as I would like.
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Jan 15, 2010
Here's the situation - Most of this ASP.NET Web Forms application (which uses a single master page for all pages) with Forms Authentication, has a standard session timeout, but there are some "modes" where we store an encoded cookie that links the user to their account.
I would like to manually check early on in the page lifecycle for the cookie, and if certain conditions are met, manually re-establish the user's authentication ticket/session.
Where's the best place to do this? Master page Page_Init? Global.asax BeginRequest?
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Sep 14, 2010
Does the OnActiveStepChanged method of an asp:Wizard control get processed after Page_Load and before Page_LoadComplete?
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