I have several "ASP:TextBox" controls on a form (about 20).
When the form loads, the text boxes are populated from a database.
The user can change the populated values, and when they submit the form, I take the values posted to the server and conditionally save them (determined by some business logic).
All but 1 of the text boxes work as intended.
The odd box out, upon postback, does not contain the updated value that the user typed into the box.
When debugging the application, it is clear that myTextBox.Text reflects the old, pre-populated value, not the new, user-supplied value.
Every other box properly shows their respective user-supplied values.
I did find a workaround.
My solution was to basically extract the text box's value out of the Request.Form object: Request.Form[myTextBox.UniqueID], which does contain the user-supplied value.
What could be going on, here?
As I mentioned, the other text boxes receive the user-supplied values just fine, and this particular problematic text box doesn't have any logic associated to it -- it just takes the value and saves it.
The main difference between this text box and the others is that this is a multi-line box (for inputting notes), which I believe is rendered as an HTML "textarea" tag instead of an "input" tag in ASP.NET.
Are you initially loading the data only when !Page.IsPostBack? Also, is view state enabled for the text box?
this happens to me all the time.
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
// populate text boxes from database
}
}
I would second Jonathan's response I would check your databinding settings.
If you do not need ViewState for the textboxes (i.e. no postback occurs until form submit) then you should disable it.
It sounds like you are not having problems saving the data (since you said you have managed to get the control to read the correct data back). Therefore, I would say the problem loads in your databinding code.
Remember the order of the page lifecycle, and where you are databinding your form.
PreInit
Init
Load
Your Control Event Handler
If you are reading the value in the Control Event handler, yet databinding in Init or Load, you'll have the old value.
The trick is to always databind in the correct event, or check for postback and don't databind then.
Are you initially loading the data only when !Page.IsPostBack? Also, is view state enabled for the text box?
I had almost forgotten to check the ViewState, but ended up remembering to verify that it wasn't disabled before making my post here on SO. I even set EnableViewState="true" to make sure.
I did find the solution, and it coincided with most of the answers here. The form was indeed loading its data more than once (which is intentional behavior). I implemented some special code for this field, and all is well.
Thanks for your replies, all!
Related
Scenario: I am having a user control which has two drop down lists. The values of the second drop down is fetched and populated depending on the selection made in the first. So, the first drop down makes a postback and pulls the data for the second. The second dropdown, therefore, does not need any postbacks on any selection changes.
This user control is being used on a page in a gridview, and therefore it repeats several times depending on the number of records in the grid.
Problem: When I make a selection in any of the dropdowns, my previous selections in all the user control dropdowns are lost and reset to the first item in the dropdown list.
Solution that works for me: I am able to fix this behavior by setting the selections made in viewstate on SelectedIndexChanged event for the respective DropDownList. But I want to avoid the postback being made by the second dropdown as it does not do anything related to UI (changing or pulling additional data to update on screen) and from the user perspective, its a waste of time and thus irritating.
I have also tried using javascript to write the values I want to persist into hidden fields, but the hidden field values are empty when the page is refreshed.
So, What is the best way to persist the dropdown values without having to postback or to write server-side code?
Thanks in advance.
#Aniruddha , I guess you are filling the first dropdown at the page load of UserControl so write that code in !IsPostBack constraint, i.e.
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack){
// Write your existing drop down bind or other code here.
}
}
Aniruddha you are probably binding you grid in the Page_Load and so in this case bind the grid under constraint of !IsPostBack as above
Hope this will help you !!
I have a fairly complex form (user control actually) with one textbox control on it that needs to NOT post back. Is there a way to remove a control from the post? Yes, this textbox is editable.
More info: This is for a credit card processing form, so the "final" submit will post to another site's page. However, prior to this there is plenty of server-side processing that goes on. I know that I can move the the credit card number text box to another page - but this requirement came very late and I'll trying to not have to re-work a lot of things.
The easiest way would be to use an html input as opposed to an ASP TextBox. These are not accessible from code if runat="server" is not set on them.
Or use the viewstate property (http://msdn.microsoft.com/en-us/library/system.web.ui.control.enableviewstate.aspx)
So the situation is that you have a form that is rendered in the user's browser with an action pointing to a different site and you need to make sure that one of the form fields will not be sent when the form is submitted.
Sounds to me like you cannot in that case make absolutely sure that the value is not posted. There are many different possible ways to solve this using javascript (disable input, clear value, etc before submit) but if scripting is turned off I think you're out of luck.
But since you can prepare for sending the form to the other server (change action on form or enable button with PostBackUrl), I guess you could also then set the Enabled property on the textbox to false. That would mean that it can no longer be edited on the final page beforr posting to the other server. Or you could hide the textbox a (so it's not renered at all) and show the field as a label or literal instead.
But even then you still have to somehow make sure the secret value is not included in the viewstate of the form. Which it will be in case you use a label or literal. And also for a textbox that was disabled or hidden on the last postback. Normally the viewstate is just a base64 encoded string so it would be trivial to find the credit card number from there. You could probably fix this by turning off viewstate for the control in question (or even for the whole page) in the last post back to your page before setting the form up for posting to the other server.
If you cannot tell for sure which will be the last postback to your server, then I think you're out of luck without more significant changes. Sorry to be a downer. Some seemingly trivial things are just hard with Asp.Net web forms.
Maybe you could add a separate page that you populate with just the data that you need to send to the other server and have that a sort of "Confirmation page". In that page you could turn off viewstate, show all the data summarized (using labels and literals etc) and the actual data to post could be included in the form as hidden fields. Then that form would post to the other server when the user "Confirms".
I'm trying to persist the contents of a textbox through a postback, and I've exhausted all of my effort but can't get it working right.
What should happen is:
User selects a radiobutton
Depending which button was
selection, a usercontrol is loaded
to specify some data and a viewstate
to say which enum type it's
equivalent to.
When they click
save, if the UserControl is just a
textbox input - the simplest), the
contents are read and saved, then
saved to the database with the
format(the radiobutton choice) so
they can be deserialized again
later.
The page posts back, and
the value and format are read from
the database, then the right control
is loaded.
The problem is - the first time the page posts back, it works. Every other postback it resets to the default value of the textbox.
I have a very similar setup elsewhere, so I'm thinking it might be a minor thing I'd never think of. There's a lot of code, so it might be easier to talk about what to do (load the dynamic control, populate the values etc) rather than how to do it.
There was actually a bug in my original code which meant it would never have in the way I was using the modified version. Apparently state is restored in Page_Load, so any controls need to be initialized by to have their values restored.
Creating the control in Page_PreLoad, then populating it after Page_Load solved the problem.
I have a problem with a Dev Express component, namely AspxComboBox.
My context is this: I want to dynamically generate the interface for some of my business entities. I have designed a user-control that receives some metadata and, based on that metadata, the controls adds text boxes, date-editors and combo boxes to the interface. All of those controls work like a charm when they are added to the page in a non-dynamic manner.
However, when I add them from the C# code, the following Javascript line has an error:
document.getElementById("usercontrol_combo_I").setAttribute("autocomplete", "off");
"usercontrol" is the ID of the user control I'm designing. "combo" is the ID of the combo.
The error is that the element with the ID ("usercontrol_combo_I") is not to be found in the HTML DOM.
I've discovered that if I choose not to use DataBind on the combo itself (comment out any call to the DataBind() method of the AspxComboBox instance), the JS line that has the error is never rendered (is not present in the final HTML). But, if I leave it like that, any subsequent PostBacks empties the combo list (there are no more items in the combo). The datasource of the combo is a IList instance that is assigned on every page load (even if PostBack == true).
There is a post on DevExpress's support forum that reports the same problem, but, there is no answer from the team.
Anybody here had this problem and found a way to solve it?
With ASP.NET Dev if you're binding on the Page_Load events, you need to bind in ALL requests back to the server, this includes Callbacks as well.
Now getting the HTML element and setting its attributes isn't supported. The only supported way to turn autoComplete off is for a callback to be sent to the server and turn off autoComplete on the server-side property which will update the control. Now the comboBox MUST be the one to perform the callback or wrap the box in a CallbackPanel.
Are you setting the ClientInstanceName of the ASPxComboBox too?
Actually, I've just found a simple workaround.
If I just call DataBind() on my generated control in the page_load event of the page itself, the problem is gone.
For example:
protected void Page_Load(object sender, EventArgs e)
{
base.Page_Load();
this.control.DataBind();
}
Where "control" is a UserControl that contains the combobox.
The weird thing is that I call DataBind even on PostBack and CallBack.
But, hey, it works.
I suppose that there are still a couple more things that I miss when using Devexpress.
But "practice makes perfect" !
Thanks for the reply.
How can use a dropdown list without the autopostback=true.
The value on the server is not being changed according to the one selected from the client side. As I already stated I do not wish that for each dropdown I have the autopostback will trigger a post back.
Any time I have lost the value of the drop-down it is because I messed up and repopulated the drop down before handling the value change. For me, it has been drop-downs that I need to do something special with like add item attributes for Javascript, etc. This is data that needs to be added on every page load (aka data that is not persisted in the drop down like the names and values of each item). In these cases I have done this work on load, then I try to retrieve the value later in the page lifecycle and DOH!
Here is the page lifecycle:
http://msdn.microsoft.com/en-us/library/ms178472.aspx
Dollars to donuts that is what is happening. You are probably just reloading the items before you get to handling whatever postback event you are using to grab the value. If you are doing this and cannot get around this work flow, just save the selected index at the beginning of the logic that populates the drop-down, then set the selected index of the drop down with that value when done.
it'll be saved in the viewstate, so the value will be correct when you do eventually post back, and if you're really desperate to get the current value without a postback, javascript would be the way to do this.
Worst case you can grab the value right off the request object:
string selectedID = Request[DropdownControl.UniqueID];
You should make sure you are only filling the select box with options during the initial page load, and not again during the postback
if (!this.Page.IsPostBack) {
//fill select box here
}