DropDownList Empty On Postback?
Dec 2, 2010
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:
<asp:DropDownList ID="RoleList" Width="100px" runat="server"></asp:DropDownList>
I am then populating the List in the Page_Load Event:
protected void Page_Load(object sender, EventArgs e)
{
RegisterUser.ContinueDestinationPageUrl = Request.QueryString["ReturnUrl"];
[code]....
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Similar Messages:
Aug 26, 2010
I'm working on ASP.NET 4.0 and I'm having problems for saving the selected value in a DropDownList.
I initialize it in the Web Control's PreRender method as follows:
if (!Page.IsPostBack)
LoadCountryList();
Where LoadCountryList's code is:
private void LoadCountryList()
{
var vr = new CountryRepository();
var countryList = vr.GetAllForList();
DdlCountry.EnableViewState = true;
DdlCountry.DataValueField = "code";
DdlCountry.DataTextField = "name";
dlCountry.DataSource = countryList;
DdlCountry.DataBind();
}
After I submit the form, I've noticed the DropDownList is empty(it's not before postback). If you take a look at my code, I've enabled the ViewState for this control, but I'm not getting any results yet. Does anybody know what's going on?
EDIT:
Here is the simple code of the control in the aspx file:
<asp:DropDownList Runat="server" ID="DdlCountry">
</asp:DropDownList>
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Sep 15, 2010
A form contains 2 cascading dropdowns. When an item is selected in the first dropdown, jQuery retrieves a list (json) from the server and fills the 2nd dropdown.
The user posts the page to the server, and when the page is returned the dropdown is empty because its not stored in viewstate.
What do you do in this situation? Is this the point where cascading dropdowns using jQuery and trying to make your page a little more stateless gets tedious?
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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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Nov 17, 2010
I have a FileUpload control inside of an update panel that I would like to use to do async file uploads. The issue I am having is that during the partial post back, the FileUpload control is empty. I was under the impression that through an update panel doing the full page life cycle that it would pick up the use input.Am I incorrect here? Can this somehow be done or do I need to do the traditional full page post back to get this to work?
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Mar 22, 2010
I had a page inside a master one the page is like
[Code]....
[Code]....
and my code behind
[Code]....
On debugging I noticed that no values are taken from textbox and in postback the textbox is cleared.
I worked in viewstate stuff and enabled it for the textbox and page, but with no results.
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Jan 13, 2011
i have this citys in my database:
city1
city2
city3
city4
i what to see this in my DropDownList:
[empty]
city1
city2
city3
city4
this is my bind code:
SQL = "select distinct City from MyTbl order by City";
dsClass = new DataSet();
adp = new SqlDataAdapter(SQL, Conn);
adp.Fill(dsClass, "MyTbl");
adp.Dispose();
DropDownList3.DataSource = dsClass.Tables[0];
DropDownList3.DataTextField = dsClass.Tables[0].Columns[0].ColumnName.ToString();
DropDownList3.DataValueField = dsClass.Tables[0].Columns[0].ColumnName.ToString();
DropDownList3.DataBind();
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Sep 16, 2010
I'm using the new Aurigma Image Uploader Flash control, and creating sample pages works great. However, when I drop this control onto an existing page on my existing site, it doesn't work. I can only suspect something in the masterpage or something else on the page is messing with it.
POST http://localhost:15361/myaccount/placead/new.aspx?postFiles=1 HTTP/1.1
Host: localhost:15361
Connection: keep-alive
Referer: http://localhost:15361/WebResource.axd?d=lAdTukuIRYXXlkVPS6yEQZdE0ZRhHxifFcDrPbzU_MDuk0OznXELaqd3rcUkbR18raDHqf4pWx6gUcGn391SmV3WbAt2TQUplpFdDsAU-K_ZPuSQ_dytDj992Foht1WO0&t=634202353399418554
Content-Length: 891463
x-preprocess-required: true
[code]...
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Mar 8, 2010
My app has broken after upgrading to ASP.NET 2.0. The problem is that Request.QueryString is empty when the SelectedIndexChanged event of a IE Web Controls tab strip is fired. It worked perfectly in ASP.NET 1. I have the tab strip contained within my own UserControl.
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Jun 15, 2010
I add HTML and tags to Page dynamically. But after every postbost, all values are empty. What can I do for Solve?
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Jan 17, 2011
I have a custom control that has a hidden field. Upon postback I want to obtain the value stored in it, but it's always an empty string.I am performing client-side manipulation of the hidden field values and have verified in firebug that the fields are correct before issue a post back,Here is the setup:
public class DualListPanel : SWebControl, INamingContainer
{
protected IList<DlpItem> UnassignedList { get; set; }
protected IList<DlpItem> AssignedList { get; set; } [code].....
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Sep 13, 2010
I m using MultiView and View Controls in my site. I have placed some DropDownlists in different Views containing data of YES/NO or some other data. I have put that data manually by Edit Items. But when i run the project my all DropDownList shows empty.
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Feb 9, 2011
A web site project, 4 pages. First page just has button links to redirect to another page. When button link is cliced, the data is retrieved from SQL Server through stored procedures and they are in a class file. Able to call the procedures and pass the information through SET Properties and right before the page is displayed, checked and data is in the dropdownlist control then redirect to show page. The dropdowlist is empty, should I be using something different to show the page with the data? Have tryied REDIRECT and then fill dropdownlist and its still empty on displayed.
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Mar 22, 2010
I have an ASP .Net TreeView control that I am dynamically adding tree nodes to from my codebehind on Page_PreRender. The TreeView is populated nicely and the appropriate checkboxes are where they are expected to be. For each of these nodes the SelectAction=TreeNodeSelectAction.None. However, when accessing the TreeView CheckedNodes() collection in my codebehind after selecting a few nodes (checkboxes are selected) and clicking a submit button to post back to the server in the button click event, my CheckedNodes.count() = 0. I can not figure out why my CheckedNodes collection in the codebehind does not contain the nodes that I have checked from the GUI.
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Apr 27, 2010
I'm trying to generate a dropdownlist in a GridView. However, my dropdownlist seem to be empty and I'm not sure how to fix it. Here's my code for the dropdownlist in my GridView & it's SqlDataSource.
DropDownList in GridView:
SqlDataSource for DropDownList:
[Code]....
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Mar 26, 2011
i have a dropdownlist that bind with sqldatasource1. everytime i load this page, dropdownlist will display directly the content of data.
However, what i want is display empty message like --Please select your currency-- by default.
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Nov 20, 2010
This code is used to render the first line empty.
[Code]....
return this error:
Sys.WebForms.PageRequestManagerServerErrorException: Exception has been thrown by the target of an invocation.
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May 7, 2015
I add this code but textbox value show in empty in database .. On Button Click the GridView TextBox loose all data ..
public partial class keyexam2 : System.Web.UI.Page {
//SqlConnection con = new SqlConnection(@"Data Source=.SQLEXPRESS;AttachDbFilename=D:shubhangijayonlinepaperApp_DataQUIZ.MDF;Integrated Security=True;User Instance=True");
DataTable dt = new DataTable();
//DataRow row = dt.NewRow();
[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.
Now, the requirement is:
As the user selects a category from the first dropdownlist, the second dropdownlist should populate based on the selection just made.
The road-block:
This should be done without a postback. My boss wants something like the drop downs on this page.
So what I gather is, I'd have to retrieve the data from the database on page load event, store it in the cache(or somewhere else?), then use javascript to handle the selectedindexchanged event of the 1st dropdown, use the data from database stored at pageload and populate the second dropdown according to the selected value of first dropdown.
P.S.- I'm a beginner ASP.Net C# programmer and have no knowledge of Javascript.
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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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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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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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