In ASP.NET webpage, I have set the EnableViewState to false to the page and all the controls of the page. Still I am getting the PostBack data in the Controls.
Is there any way to remove this?
How do we remove the page life cycle event like restore PostBackData?
Actually _ViewState is maintained for all controls. I am not clarified from MSDN as well.
Postback data has nothing to do with ViewState.
If you don't want Postback data, why are you using Post? What are you trying to achieve?
Because you re-bind your datas after each PostBack
You can use !IsPostBack in your Bind
if(!IsPostBack)
{
//Bind your datas just for load, and disable your ViewState, that will erase your selected datas
}
Related
I am trying to take advantage of the page lifecycle in Asp.NET so that I don't bind to my datasources more than I actually need to.
This has led to the following problem. I have an ObjectDataSource, GridView, and a button on my page. The button adds a record to the database, which should be picked up by the data source and presented on the Grid. The problem is that the item is not showing up on the gridview until I refresh the page.
I can solve the problem by calling GridView.DataBind() in my button's event handler, but this goes against what I understand about the .NET Page Lifecycle.
Based on this article, the lifecycle should be as follows:
In addition the article states that the Databinding event is "Raised after the control's PreRender event, which occurs after the page's PreRender event."
So, my button click event should fire first, during the Event Handling phase. It should add the record the database.
Next PreRender should be called on the controls.
Finally DataBind should be called on the controls, and the Grid should update to capture the new record.
Yet this doesn't seem to happen. What am I not understanding?
I think the issue is that your viewstate is not enabled on your GridView. This is what I experienced, but then I also had to call DataBind() on the GridView from the page PreRender event if the request was a postback to get the data updated in the GridView on postback.
Edit:
It would help to understand the issue and context better if you could post the source code of your page (aspx + codebehind). How and where do you connect your GridView to your datasource? Statically in markup or dynamically? Do you make any calls to page.DataBind()? ... These things may influence the behaviour of the GridView.
I have a textbox, that programatically i set it 'Enabled = false'. When the page, after this change, get a postback, this textbox return the enabled value to true. why?
I have the textbox into a updatepanel.
If you're setting it in code-behind in the Page_Load event, you need to remember that Page_Load occurs even on postbacks. You have two options.
Place it with in a block that checks to see if the page is a postback.
if(!Page.IsPostBack)
{
TextBox1.Enabled = false;
}
or set it in Page_Init instead.
If you're not already familiar with it, be sure you understand the Page Lifecycle. This is must-know information for ASP.NET developers. Read about it at http://msdn.microsoft.com/en-us/library/ms178472(v=vs.100).aspx
In the page_load, do the following:
If (IsPostBack) Then
Textbox1.Enabled = False
End If
I forgot to mention this asp.net 2.0.
The user control has a unique id and it is loaded in the PageLoad event.
The user control is loaded into a panel and the panel is inside of a webpart.
The dropdown has autopostback set to true.
EnableViewState = true on the dropdown.
The ListItems are created in the dropdowns pre-render event method.
This is why I don't understand why it is not firing, the dropdown is the only thing that causes postback on this user control.
The event methods for the dropdown should occur since the user control is loaded in the page load method on postback again right?
Make sure there is no OnLoad or PageLoad event that is rebinding the datasource of the dropdown list. Rebinding the data with a new set of data may cause the clickhandler to not ever get executed.
make sure you have if (!Page.IsPostBack) around dropdownlist.datasource = and dropdownlist.databind()
I am not sure if this is your problem, but it is the most common.
Try with EnableViewState set to
true for the DropDownList
If the ViewState is set to false, on post back the selected Index gets back to default which is normally the first Item. First item, if selected, does not cause SelectedIndexChange event to fire
I am having a listbox in ASP.net. I am populating the listbox values from another listbox in a page dynamically. During postbacks the values of output listbox are not persisted.
(while going to another page and come back to this page).
Please suggest some good answer. EnableViewstate = "true" is not working.
Are you doing anything in Page_Load that should be in a
if(!IsPostBack) {}
Initialization code in load needs to only be called when the page is first loaded, not on postbacks.
If you are going to another page and then coming back to this page, I think you need to preserve the information yourself in the Session and then restore it when you come back to the page.
The viewstate is only preserved as long as your on the same page doing postbacks.
As Lou Franco wrote
if(!IsPostBack) {}
You use this on the initial pagerequest to fill in the data. if you wish to preserve the data across pages using the session to store the values is the best bet.
preferably you fill in the data in your listbox before the SaveViewState event thats in PreInit as far as I recall.
Initialize the content of your controls in your Page's Init event (Page_Init). That way any values the user supplies are not overwritten by your defaults.
EnableViewState will just repopulate the output listbox with the values that it had when the page first rendered, since they're still the ones stored in the viewstate. The browser sends only the selected value in the postback, so there's no way for the server to know what other values you added on the client.
You can work around this by adding a hidden input to the page and populating it with the dynamic values when you update the listbox. Your page can then check that value during a postback and repopulate the list properly.
Changes made to the listbox on the client side are not persisted during a postback, you need to record that information in hidden fields and then configure the control during the page_load event to make the changes stick during the rest of the postback.
I'm writing an ASP.Net webform with some DropDownList controls on it. Then user changes selected item in one of dropdowns, ASP.Net doesn't seem to handle SelectedIndexChanged event until form is submitted with a 'Submit' button click.
How do I make my dropdowns handle SelectedIndexChanged instantly?
P.S. It's a classic question I have answered too many times, but it seems no one asked it before on stackoverflow.
Setting the AutoPostback property to true will cause it to postback when the selection is changed. Please note that this requires javascript to be enabled.
You need to set the AutoPostBack property of the list to true.
Also, if you're populating the contents of the drop down list from the code behind (getting the contents of the list from a database, for example) - make sure you're not re-binding the data in every postback.
Sometimes people are caught out by binding the drop-down in the page load event without putting it in an If Not IsPostBack. This will cause the event not to fire.
The same is also true of repeaters and ItemCommand events.
if you are populating the dropdown list during page load then each time the page postback it will reload the list thus negating your postback method.
you need to be sure to load the dropdownlist only if (!ispostback)
Set the AutoPostBack property of DropDownList to true.