C# - .net DropDownList Gets Cleared After Postback?
Jul 8, 2010
This has been driving me nuts all day. I've seen this problem crop up here a few times, essentially I have a drop down list that populates a form below when it's changed - basic stuff. On first page load everything is fine, but when the dropdownlist is changed, it's entirely blank after postback and the SelectedIndexChanged event never fires. I believe it all points to a viewstate problem. Here's the code..
<%@ Control Language="C#" AutoEventWireup="true" CodeFile="EditUser.ascx.cs" Inherits="Controls_EditUser" %>
<asp:DropDownList OnSelectedIndexChanged="SelectedIndexChanged" AutoPostBack="true" ID="UsersList" EnableViewState="true"
runat="server" DataTextField="EXTRANET_USER_EMAIL" DataValueField="EXTRANET_USER_ID">
[Code]....
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Nov 28, 2012
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<%@ Page Title="" Language="C#" MasterPageFile="~/MobileMaster.master" AutoEventWireup="true"
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[CODE]...
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Mar 18, 2011
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[Code]....
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[Code]....
[Code]....
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Aug 10, 2010
I have a .aspx page having two dropdowns, the data to be loaded in them is usually static(but may change everyday), the first dropdown always displays the main categories and the second dropdown is initially empty.
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The road-block:
This should be done without a postback. My boss wants something like the drop downs on this page.
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Aug 26, 2010
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if (!Page.IsPostBack)
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Where LoadCountryList's code is:
private void LoadCountryList()
{
var vr = new CountryRepository();
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}
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EDIT:
Here is the simple code of the control in the aspx file:
<asp:DropDownList Runat="server" ID="DdlCountry">
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I've looked at answers to some similar question but I still can't seem to figure this out. I think I'm misunderstanding something about how ASP.NET works.In the standard ASP.Net 4.0 'Create a new Account' form, I've added a DropDownList containing Roles to be selected for the new account. in the aspx page, the control looks like this:
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Mar 25, 2010
I have the following within an updatepanel. If i make a selection somewhere else that has its own updatepanel, this data gets cleared.
[Code]....
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I have a wizard control with 3 wizard steps. 1 contains "create new user", 2 for user management grid control and 3 for another functionalities.My problem is.. I am able to create new user successfully and after clicking on continue button in create new user, the name, email id text fields are not getting cleared.
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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]....
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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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Feb 15, 2011
This is fine with a single textbox, but I want show different value from database into different textboxes.
How can I do that?
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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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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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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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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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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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Mar 28, 2011
I have an asp.net dropDownList listing hours and minutes of the day. I want the time chosen to be shown in a texbox. Can this be done without making a postback?
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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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