Web Forms :: DropDownList Doesn't Postback?
Sep 22, 2010
I've created two datasources, one that gets a list of categories and it's id's and the other one get subcategories and it's id's. The categories are presented in a DropDownList and the subcategories in a ListBox. When choosing a category from the DropDownList the ListBox presents the subcategories of the chosen category. The subcategory datasource is set to get it's value for what category to get from the DropDownList's selected value.
My problem is that when I change the category in the DropDownList the subcategories doesn't update on a postback. Instead I have to press a button on the page that I know performs a postback to get the subcategories to update. What am I doing wrong here? I'm using this method on another page as well and when comparing them I can't find anything different. Any ideas?
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Jan 18, 2010
I have just found the solution. The following function works (remove the else part):
function confirmSubmit() {
if (Page_ClientValidate("Group1")) {
return window.confirm("Are you sure to submit the form?");
}
}
But I am wondering why it doesn't work when I add the else part.
Question:
I want to have a confirm dialog after user fills in all the data in the form. I set onclientclick="return confirmSubmit()" in the submit button.
function confirmSubmit() {
if (Page_ClientValidate("Group1")) {
return window.confirm("Are you sure to submit the form?");
} else {
return false;
}
}
If Page_ClientValidate("Group1") returns false, the dropdownlist doesn't cause postback after I first select the item, and the postback only occurs when I select the dropdownlist second time.
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Aug 6, 2013
I have two dropdownlists on my page that are related to one another, and are built dynamically. I did not write the original code, but I believe it is using AJAX so the whole page doesn't postback when the ddl selection changes. The first ddl is Status and the second is ContractType. Here is the code for the event handler:
Code:
protected void Status_SelectedIndexChanged(object sender, EventArgs e)
{
try
{
DropDownList status = (DropDownList)sender;
string selectedStatusId = status.SelectedItem.Value;
[Code] ....
Here is some of my debugging info:
? view.Count
4
? view.Table.Rows.Count
20
? contractTypeDropDown.SelectedValue
[Code] .....
I commented out the event handler since this snapshot, just to see what would happen, but when I was hitting it you can see what ex.Message was. I don't understand why it says the SelectedValue is invalid when I see the selected value is "E " and that is one of the four items in the ddl.
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Mar 22, 2010
In my project when i click any button or linkbutton, it doesnt fire any event or doesnt postback.
It was working fine but now it hv problem like this.
I think i have changed some settings by mistake.
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Mar 25, 2011
I had use a combox to let user select staff name and then it will automatically retrive the responsible recommending officer and approving officer to display in other 2 dropdownlist.
my code works fine but when user select staff name each time, the page will reload once to refresh the dropdownlist.
user complaint and don't want the page reload every time, how can i disable the postback? I need to use ajax?
[Code]....
[Code]....
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Dec 29, 2010
[Code]....
Then, in the codebehind I have this code:
[Code]....
This works fine when I display the page. However, when I click the language link which causes a postback the content block does not get added to the placeholder, so I get a null reference because those two panels don't exist. I've been pulling my hair out over this for a few hours now and I can't figure it out. In case it helps, here is my InitializeCutlture method:
[Code]....
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May 13, 2010
I've some really strange behaviour with a simple ASP.NET Button. Here's my code:
[Code]....
For some reason the first time I click this button, the code is beeing fired. When login credentials are wrong, a message shows up. THen, the user inserts the right credentials. After clicking the 'cmdLogin' button, nothing happens and the old (wrong) values are beeing filled in inside the textboxes. This behaviour occured to me after switching to ASP.NET 4.0.
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Jul 19, 2010
I have a dropdownlist, who's items I bind from the codebehind file of an asp.net web page. After databinding, I want to set the selected index as the last item in the list, thus:
[Code]....
However, this does not work. When the page is done loading, the selected index is still zero.
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Sep 29, 2010
I've got two DropDownLists that are filled using a couple of SqlDataSources, like so:
[Code]....
The third DataSource, dsCriterias, is used to present a set of dynamically added DropDownLists depening on what's selected in the second DropDownList, subcategories. The set of dynamic DropDownLists are presented using this code:
[Code]....
The code works but there's little thing that's bugging me. When the page is first loaded the criterias belonging to the subcategory is not presented. I expect it to show the criterias but ther won't show until I make a choice in the categories-DropDownList meaning if I wan't the first subcategories criterias I have to choose different subcategory and then go back to the first one. It's a bit hard to explain.
An example: When the page is first loaded I get a category presented, eg. Vehicles. In the subcategories I get the alternatives "Bicycles", "Cars" and "Motorcycles". "Bicycles" will be the one presented when the page loads since the stored procedure used by dsSubcategories sorts the data by the subcategory names. The problem is that I don't get the criterias for the "Bicycles" subcategory at page load. To get them I first need to select "Cars" or "Motorcycles" and then choose "Bicycles".
I've tried putting a subcategories.SelectedIndex = 0 in in the OnLoad but nothing seems to do the trick.
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Aug 10, 2010
I have a dropdownbox which does an autopostback when selected index has changed. But the selected value never changed.
[Code]....
[Code]....
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Jan 21, 2010
[Code]....
here's the code I use after the selectedindexchange
[Code]....
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Apr 29, 2010
I have already spent two day to solve this on my own but for some reason I can't. Maybe I'm missing the live cicle of the dropdownlist. I hve a three dropdownlist that filter a gridview and the other two dropdownlists One is "Year" the other is "Country" and the other "Species" Each one of them is filter by the other two. So if I filter for one year it will only show me the species and countries that have records on that year. So I have to reload the gridview and all the dropdownlist.
What happend is that since I'm filling again the dropdownlist with less values he can't remember the previous one. I have tried with the events: DataBinding, Load Unload and Init of the dropdown list to force it to remember. The conclusion I have reach is that the databinding and the load have the dropdown list of the previous page. So if I do
String strYears = ddlYears.SelectedValue.ToString();
ddlYears.SelectedIndex = ddlYears.Items.IndexOf(ddlYears.Items.FindByValue(strYears));
And the year was on the index 4 but after changing the country the year is now index 3 he mantains the index 4 showing me another year.............................
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Jun 29, 2010
I have a dynamic dropdown that is populated from sql. The user is supposed to select an option from the dropdown, then click a search button on the form to return some results based on that selection. It works fine if the dropdown gets populated with more than one record. However, if only one record is returned, that one record can't be selected. Whether you select it or just leave it alone since it's the only one, when you click the form button (search button), no results are returned b/c the dropdown selection must not be actually selected.
I've included the relevant code below. First the DDL, then the datasource, and finally the C# code in the if (!Page.IsPostBack)
[Code]....
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Apr 6, 2010
This would be a simple one for me if I was binding this dynamically. I don't think it's necessary to have a code behind for only 4 or so values. Anyways here is my ddl.
[Code]....
The problem is that when a user selects a value and it postbacks my ddl resets to the first value. How do I prevent this?
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Aug 3, 2010
I have 5 dropdpwnlist in asp.net page.. the 5th dropdwpnlist will show data based on 4th dropdownlist. and 4th dropdwpnlist will show data based on 3rd dropdownlist. and 3rd dropdwpnlist will show data based on 2nd dropdownlist. and 2th dropdwpnlist will show data based on 1st dropdownlist... All dropdownlist has auto postback=true.. so it cause postaback each time.. i want to avoid postback coz it refresh all page again and again and shows data.. coz my aplication is in hosting server..
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Nov 12, 2010
I created a dropdwonlist and add colours to the items. But the colours will lose after the postback. After googled, I knew it is because the attributes specified for the dropdownlist were not saved in ViewState and also found the code to Overriding SaveViewState() and LoadViewState(object) from [URL]
But after I copy the code to my web application to create a new class, there are so many error massages. I have spend two days to find the solution, without much success.
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Apr 1, 2010
I have a situation where i want to postback and redirect the user to the diffterent page wherever the user selects something from dropdown list. If the user presses the back button the in the browser the dropdownlist should be in the default state. i have already tried this code
protected void ddl_SelectedIndexChanged(object sender,Eventargs e)
{
int selecteditem = int.Parse(ddl4.SelectedItem.Value.ToString());
ddl.ClearSelection(
ddl.Dispose();
//Even tried ddl.selectedindex = -1 ;
//dosome postback i.e redirecting the user depeneding upon the value in selecteditem
}
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Mar 1, 2011
I would like to expand dropdownlist after onfocus postback. There is some code that runs when OnFocus is fired off then it needs to stay expanded so the user can select an item from dropdownlist. Currently it expands and contracts real fast when user clicks the dropdownlist, then the user has to click it again to select an item.
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May 10, 2010
I am having trouble with a dropdownlist and it's values not getting updated after postbacks.
Situation: I have an ASPX page that contains 2 user controls (UC1 and UC2). When the page first loads, controls on both UCs are set properly. My problem comes from the fact that when a dropdownlist on UC1 is changed, I need to reload a dropdownlist on UC2 (based on
the new value). I am raising an event from UC1 to the parent page when the dropdownlist value is changed and inside this method I am telling UC2 to reload it's dropdownlist based on the new value. When stepping through the sequence of events using the debugger, the values in the datatables and dropdownlists (item count) are 100% correct but after running through the logic, the dropdownlist on the page still has it's old values.
The initial values for the dropdownlist in UC2 are populated in Page_Load of the ASPX page, and nothing is done to the dropdownlist in Page_Load (!Page.Postback) of either the ASPX page or UC2. The only way I would like the values to change is when the event from UC1 is raised back to the page.
I have found a couple of other forum posts out there that had the same problem but I've tried those resolutions and nothing has worked. In the following examples, the value dt is the 'new' datatable that I wish to bind to the dropdown.I read that before rebinding the dropdownlist, that the Items need to be cleared and the SelectedValue should be set to NULL:
this.dropdownlist.DataSource = dt;
this.dropdownlist.Items.Clear();
this.dropdownlist.SelectedValue =[code]....
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Nov 29, 2010
i have two radio button list on my page on my Frist Index there is a panel with Drop Down List and on Second Index there is a static variable in which i am storing value as Pending
now as soon as i select my Second RadioButtonList it also stores the DropDown List Value
how i can clear the DropDown List Value?
My Code
[Code]....
My Page Source
[Code]....
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Oct 19, 2010
I hve few values in my Drop Down List
[Code]....
i want when ever i Select the Value-"Select " it should not postback it PostBack me when ever i Select the value ("Select Again")
can't use Ajax right now other alternative would be javascript
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Feb 25, 2010
Using VS2008, .NET 3.5, and C#. The page contains (among other things) a dropdownlist and an objectdatasource. The Page_Load event fires the objectdatasource's Select event. The Selected event iterates through the returned datatable, feed each row into a ListItem, checks to see if a certain column is True or False and, if true, changes the styling for that row to color:red. Finally, the listitem is bound to the dropdownlist. The end users sees all of the dropdownlist items that are false in black and the items that are true are in red. Works perfectly. However, as soon as any item is selected, the page does a postback and the font colors in the dropdownlist revert to the default black. Is there a way, other than rerunning the method that iterates through table and creates the listitems, of maintaining the coloration of the items? Is there a ViewState setting or something?
Here is the dropdownlist and objectdatasource's Selected event:
[Code]....
[Code]....
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Mar 10, 2010
i have dropdownlist with autopostback=true,
written onchange event for confirm popup and SelectedIndexChanged event also exists.
req is if confirm returns true then only postback should happen else not
instead its not atall doing postback whether it returns true or false.
i managed to get it work by forcing postback by using __doPostback()
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Feb 23, 2010
I have 2 - DropdownList controls, which i am filling at severside when page loads. After the user selection in DropdownList1, i am changing the contents in DropdownList2 values. This validation (i.e. changing the contents of Dropdownlist2 values) am doing in Javascript Clientside. But on postback i am not getting the values in DropdownList2. When i say "DropdownList2.Items.Count;" getting "0". I tried to put the contents of DropdownList2 in ViewState on pageload. But i am getting Serialization error at runtime "Viewstate["PersistValues"] = DropdownList2;". I am using html input hidden control to pass the values from server side to clientside for my validation. Now, to meet this requirement i am Binding the DropdownList2 at postback again with first DropdownList1's selected index (This is repeat of logic which i have done in Clientside).
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Oct 19, 2010
I have been having some trouble with dropdown lists reverting back to selecting the initial item in the list after a postback once a selection has been made from the dropdown list. I have read up on this and found out that a "if not ispostback then" is required.This works fine when I add in all the items in the dropdown list manually like:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not IsPostBack Then
ddl1.Items.Add("Select...") [code]....
However, I have over 250 items and so it is far more efficient for me to load then in by using part of a multidimensional array which is created from a text file - Definitive database.txt. I have been using the following code to do so:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not IsPostBack Then
'loads the definitive database array[code]...
This loads all the items into the dropdown list perfectly, but now every time a selection is made, it reverts back to the inital item on postback even though i have included the "if not ispostback then" part.
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