ASP.Net suppress postback for combobox only for OnSelectedIndexChanged - javascript

I am using an AJAX ComboBox in my ASP.Net web application and I have an OnItemInserted event that requires a postback to hit the server side logic however this requires that I have AutoPostBack = True. This causes an unwanted effect of OnSelectedIndexChanged event triggering a Postback causing the control to lose focus.
More background: This combobox resides inside of a fairly complex gridview which contains other comboboxes, dropdownlists, and textboxes. My objective is to allow the user to smoothly tab through the row while entering data without having to use the mouse to promote rapid data entry.
I believe that I need to utilize javascript to suppress this postback but I am open to suggestions.

You can suppress the postback by simply returning false on the relevant client event:
http://edgewaters.blogspot.com/2008/01/button-that-doesnt-post-back.html

OnSelectedIndexChanged="return false"

Related

No additional postbacks work if validation fails on first postback

I have never noticed that ASP.NET automatically shuts down all subsequent postbacks until the field that validated as false is fixed by the user.
My scenario:
I have a form with 3 fields. One of them is a Textbox (txtCarName) with a required field validator and then I have a dropdown(ddlCarMake) with AutoPostBack=true, that filters and enables another dropdown (ddlCarModel) OnSelectedIndexChange.
Lets say the user clicks the save button without filling out the required textbox (txtCarName). They will be notifed that it is a required field.
Before they go and add a value to the required textbox lets say they decide to edit the ddlCarMake because they change their mind. In this case the filter does not happen since all subsequent postbacks are disabled. The user would be extremely confused.
How do ASP.NET developers avoid something like this from creating a poor user experience?
UPDATE:
After contacting Telerik they told me this is a known issue and is currently fixed in their internal build. The next release it will be fixed.
set the dropdownlist CausesValidation="False"

Dropdownlist Postback interferes with Javascript

My ASP page has a DropDownList (DDL) and a bunch of checkboxes. When my user selects a DDL item, I have some JS/jQuery code to make several checkboxes invisible according to some logic. However, the postback of the DDL, needed to run the C# code-behind event handler, causes a redraw of the entire page and makes all checkboxes visible.
How can I prevent the postback from wiping out the actions of the JS? Should I store visibility bits in something like ViewState?
Is it possible to have the JS code run AFTER the postback, instead of before?
Is it possible/easy to use CallBack instead of PostBack for the ASP DropDownList? I was thinking that the fun of Ajax was avoiding postbacks and only updating the control instead of the entire page.
Well if the dropdown posts back in the same action that you flip the switch for the checkboxes, why not then put the logic to show/hide checkboxes on the server instead of the client? You can use the hidden field approach, and that would work fine.
The callback means the UI needs updated by JavaScript. I don't know what all the postback updates, but you would have to send everything up via JSON, and refresh the UI via JavaScript. So only you can make that call.

Restore dynamic Telerik RadWindows on next postback

I'm doing some ASP using Telerik.
On my page there are 2 buttons called Create Window and Postback. The Create Window button created a new RadWindow dynamically on it's click event (client-side) by using window.radopen(). The Postback button simply does a postback. My problem is that, the windows get lost after every postback. What can I do to make my RadWindows to remain opened after a postback, including its content and position.
If there is no built-in function to restore my dynamic RadWindows, please tell me how to save current windows content to manually load it on the next postback. I thought of using a Hidden control to save my RadWindow position and content, but how can I do that (it's content is a user control with plentiful textboxes, and i don't want my customer to re-type all the textboxes).
The RadWindows are generated via JavaScript when they are first shown. You can easily check this via your developer plugin of choice. Once you show them they create their wrapper div as a direct child of the form element. This means that they have no server-side rendering and thus cannot be persisted on the server across postbacks.
What you can do is use AJAX - have the button perform an AJAX request that will update the needed content of the page, but will leave the RadWindows out of the update. Check out this help article where they explain how to use AJAX with a RadWindow: http://www.telerik.com/help/aspnet-ajax/radwindow-ajaxifying.html.

RadioButtonList SelectedIndexChange Even on pop form

Hi all I have a problem with my pop up form in javascript. I using even of RadioButtonList my pop up close. So my question is how should I use RadioButtonList Even on pop up form without closing?
This is most likely because you are posting back the form and the changes made with javascript haven't been stored in the view state.
One option would be to use an UpdatePanel (assuming you mean ASP.NET and not ASP?) around the RadioButtonList to prevent a full post back.
http://msdn.microsoft.com/en-us/library/bb399001.aspx

Client-side JavaScript ViewState Update in asp .net forms

I have stumbled upon the issue when I need to retract html controls I've added client-side using JavaScript after the postback (due to server-side validation - this is not optional).
Please tell me if the way I'm trying to achieve this is cr*p and there's a better way of doing this.
basically, what I'm doing is cloning a textbox control for up to 10 times on the page when the user hits "Add" and storing entered values from each of those texboxes in a hidden field to read from in the code behind. This works fine, however, when the server side validation doesn't pass after postback, all those dynamically added (cloned) texboxes disappear, since ViewState knows nothing about them.
I am considering 2 possible solution, both of which seem hacky:
Rebuild all cloned textboxes on document onload() using stored values in the hidden field
wrap the form in ajax update panel and place the cloned texboxes outside of it, thus, not refreshing this part of the screen on postback
now, is it possible to somehow "update" ViewState to make it aware of all the html controls I've added using client-side script? Any better ideas? I'd like to achieve this with client-side script, therefore not considering cloning textboxes on server-side, sorry.
You cannot modify the ViewState on the client side. If you do, you will invalidate the viewstate and receive an error on the postback.
In your case you might want to consider using javascript and jQuery to render the text boxes on the document ready event with the values stored in your hidden field. I'd recommend taking a look at jQuery templating, particularly if you can store your data as JSON in the hidden field (http://weblogs.asp.net/scottgu/archive/2010/10/04/jquery-templates-data-link-and-globalization-accepted-as-official-jquery-plugins.aspx).

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