What's the difference between AutoPostBack=True and AutoPostBack=False?
Taken from http://www.dotnetspider.com/resources/189-AutoPostBack-What-How-works.aspx:
Autopostback is the mechanism by which the page will be posted
back to the server automatically based on some events in the web controls. In some of the web controls, the property called auto post back, if set to true, will send the request to the server when an event happens in the control.
Whenever we set the autopostback attribute to true on any of the controls, the .NET framework will automatically insert a few lines of code into the HTML generated to implement this functionality.
A JavaScript method with name __doPostBack (eventtarget, eventargument)
Two hidden variables with name __EVENTTARGET and __EVENTARGUMENT
OnChange JavaScript event to the control
AutoPostBack = true permits control to post back to the server. It is associated with an Event.
Example:
<asp:DropDownList id="id" runat="server" AutoPostBack="true" OnSelectIndexChanged="..."/>
The aspx page with the above drop down list does not need an asp:button to do the post back. When you change an option in the drop down list, the page gets posted back to the server.
Default value of AutoPostBack on control is false.
AutopostBack is a property which you assign to web controls if you want to post back the page when any event occurs at them.
You may see this article: What is AutoPostBack?
Autopostback is the mechanism, by which the page will be posted back
to the server automatically based on some events in the web controls.
In some of the web controls, the property called auto post back, which
if set to true, will send the request to the server when an event
happens in the control
For example, TextBox has AutoPostBack property
Use the AutoPostBack property to specify whether an automatic postback
to the server will occur when the TextBox control loses focus.
Pressing the ENTER or the TAB key while in the TextBox control is the
most common way to change focus.
The AutoPostBack property is used to set or return whether or not an automatic postback occurs when the user presses "ENTER" or "TAB" in the TextBox control.
If this property is set to TRUE the automatic postback is enabled, otherwise FALSE. The default is FALSE.
There is one event which is default associate with any webcontrol. For example, in case of Button click event, in case of Check box CheckChangedEvent is there. So in case of AutoPostBack true these events are called by default and event handle at server side.
AutopostBack :
AutopostBack is a property of the controls which enables the post back on the changes of the web control.
Difference between AutopostBack=True and AutoPostBack=False:
If the AutopostBack property is set to true, a post back is sent immediately to the server
If the AutopostBack property is set to false, then no post back occurs.
AutoPostBack property:
Asp.net controls which cannot submit the Form (PostBack) on their own and
hence ASP.Net has provided a feature using
AutoPostBack = "true"
: which controls like DropDownList, CheckBoxList, RadioButtonList, etc. can perform PostBack(when clicked on it).
And
AutoPostBack = "false"
It is the by default state of controls which can perform Postback on button submit.
hai sir
There is one event which is default associate with any webcontrol.
For example, in case of Button click event, in case of Check box
CheckChangedEvent is there. So in case of AutoPostBack true these
events are called by default and event handle at server sid
If you want a control to postback automatically when an event is raised, you need to set the AutoPostBack property of the control to True.
I have a dropdownlist, in the client side, i have it's on change event. If validation is passed, it's selected inded changed event should be fired(server side). My side, the server event is not getting fired. Autopostback is also set is true.
Any suggestion ?
If you are adding the code from the code-behind (as opposed to in the ASPX or ASCX markup), make sure you add it in the Page_Init event or override CreateChildControls. If you want until the Page_Load event to add it, the ASP.NET has already initialized the control state and view state and then will not be aware that the dropdown exists, so when the postback comes it won't know what control to route it to.
Also, in this case, make sure you are always adding the control to the page, not just when Page.IsPostback==false
Make sure your page code is in autoeventwireup = true.
you can check it in your page design page on top.
if autoeventwireup is set to false your event doesn't fire. auto event will set automatically event so it is necessary to write else you have to set event on initialize state.
I was wondering specifically about whether ItemCreated or ItemBound happens first but I can't seem to find any information on the order that ListView events fire. Can anyone point me to a resource for this information?
Note: this is for the System.Web.UI.WebControls.ListView
You can test it handling both events for a ListView and setting breakpoints. I tell you the end of the story: ItemCreated is executed first.
While ItemCreated happens on every request to the page containing the ListView, ItemDataBound only get fired if your control is bound to a data source.
It may happen that you bound your control on the first request and you don't do it on postback, in this case the ViewState information is used and the event ItemDataBound is not fired.
From RadGrid for ASP.NET AJAX (not the same control but the idea applies)
ItemCreated should be hooked when you need to modify the controls inside a grid cell. ItemDataBound should be wired in order to change the data displayed inside a grid cell and its controls.
I need to add the OnClick event to asp:DropDownList control, due to the existing events don't satisfy my current needs.
Is it possible to achieve this?
Thank you very much.
What reason do you have for wanting an OnClick event on the DropDownList control? If you were to implement an OnClick server-side event on the DropDownList the user would never be able to select any of the list items. This is because in order to fire a Server-Side OnClick, a postback would be required. I.e. the user would click the DropDownList, a postback would instantly occur and they wouldn't be able to select a value.
It sounds like a case of trying to fix the wrong problem, however you could probably try and use the "onclick" JavaScript attribute and handle whatever you're trying to do using client side script and AJAX?
I am building a user registration form in asp.net. I want to check if the username is available or not on the leave event of the TextBox. I am not able to get the Leave Event of the TextBox.
Should I use OnBlur event of the Html TextBox.
Please Help.
How about using TextChanged server-side event and wrapping the whole thing in an UpdatePanel for very quick ajax functionality.
If you use this method make sure the AutoPostBack property is set to true for the TextBox control.