My code is:
private void Add_Items()
{
for (int x = 1; x < 53; x++)
{
ListBox1.Items.Add("Item" + x);
ListBox1.DataValueField = "Value" + x;
}
}
None of these items raises SelectedIndexChanged event when clicked.
Please assist.
Make sure autopostback is enabled, like in this examle:
<asp:ListBox ID="listBoxLocation" runat="server" AutoPostBack="True"
OnSelectedIndexChanged="listBoxLocation_SelectedIndexChanged" EnableViewState="True">
<asp:ListItem>1</asp:ListItem>
<asp:ListItem>2</asp:ListItem>
<asp:ListItem>3</asp:ListItem>
</asp:ListBox>
Or to dynamically populate:
Protected void Button1_Click (object sender, System.EventArgs e)
{
ListBox1.Items.Add(new ListItem("Carbon", "C"));
ListBox1.Items.Add(new ListItem("Oxygen", "O"));
}
From: http://msdn.microsoft.com/en-us/library/14atsyf5%28v=vs.85%29.aspx
First.
The ListBox1.DataValueField should not be set to every item. This property sets the field on the data object (each row) to capture the value from. Here is the MSDN link for this property http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listcontrol.datavaluefield(v=vs.110).aspx.
Next, I am assuming you have all the front end code wired up something like.
<asp:ListBox ID="ListBox1" OnSelectedIndexChanged="ListBox1_SelectedIndexChanged" runat="server"></asp:ListBox>
This has the selected changed event wired up. However for this control to actually Post the data back you need to provide one more attribute. Add
AutoPostBack="true"
To your control as.
<asp:ListBox ID="ListBox1" OnSelectedIndexChanged="ListBox1_SelectedIndexChanged" AutoPostBack="true" runat="server"></asp:ListBox>
This starts the magic. MSDN for AutoPostBack: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listcontrol.autopostback(v=vs.110).aspx
Your code is very vague, and im going to make the assumption that your ListBox has not been linked up to a SelectedIndexChanged event in the correct way.
If you are dynamically creating the ListBox link it up as below:
public void initialize()
{
ListBox lb = new ListBox();
lb.SelectedIndexChanged += lb_SelectedIndexChanged;
}
private void lb_SelectedIndexChanged(object sender, EventArgs e)
{
//Do Selected Index Changed Code Here
}
If you have a view/form with the control on, simply make sure that the ListBox's event has been set or naturally it will not trigger.
*EDIT 1
As noted in other answers your control is required to have PostBack set. You should also be checking the PostBack state of your page to ensure you are not redrawing your controls continuously, as this will keep resetting your Dynamically added controls.
Related
I try to create a dynamic table with some textboxes depending on a object List.
Then I add it in an Panel contained in UpdatePanel.
Everything works great, except that some times, the postback is async, and some times, all the page reloads. There is no rule, some times it will work twice before being full postback, and some times more. Can't find a logic with this behaviour.
Here is a piece of my aspx code:
<asp:UpdatePanel ID="udpTableDechets" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:Panel ID="pnlTableDechets" runat="server" />
</ContentTemplate>
</asp:UpdatePanel>
Here is a piece of my code behind:
protected override void OnLoad(EventArgs e)
{
generateTableDechets();
base.OnLoad(e);
}
private void generateTableDechets()
{
Table tbl = new Table { ID = "dechets", ClientIDMode = ClientIDMode.Static };
TableRow trDec = new TableRow();
tbl.Controls.Add(trDec);
TableCell tdDecReel = new TableCell();
trDec.Controls.Add(tdDecReel);
TextBox txtDechet = new TextBox { ID = string.Concat("txtDechet_", product.Nom), ClientIDMode = ClientIDMode.Static, AutoPostBack = true };
txtDechet.TextChanged+=new EventHandler(txtDechet_TextChanged);
tdDecReel.Controls.Add(txtDechet);
pnlTableDechets.Controls.Add(tbl);
}
protected void txtDechet_TextChanged(object sender, EventArgs e)
{
// Get the value, and update the object containing values
// Then update labels in table thanks to another method
}
UPDATE 1
Actually, I tried the same in static, and I have exactly the same behaviour.
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:TextBox runat="server" AutoPostBack="true" OnTextChanged="txt_TextChanged" />
</ContentTemplate>
</asp:UpdatePanel>
Is it normal for you ? Is it a known bug ? Have I forgive something ?
How can I do to be sure every textChanged request will execute asynchronously.
Thank you in advance for your answers
Update 2
The problem seems to occur when I press Enter key or when I hilight the textbox content to replace it.
Solution
I finally did it thanks to the IPostBackEventHandler Interface (see here).
I manage the event manually, and catch it in the RaisePostBackEvent() method. So here, thanks to the control ID passed in parameter, I can do my stuff.
Thank you for your answers
It is a comman issue while creating a website that contain dynamic controls.
If you want to fire event each time you should call code behind from javascript.
Since javascript is executed each time.
ex.
function SaveClick() {
Page.GetPostBackEventReference(objBtnSave);
__doPostBack("objBtnSave", "OnClick");
}
May be this will resolve your problem.
In static, I made it work adding the ChildrenAsTriggers="true" Property, or specifying an AsyncPostBackTrigger on each dynamic control with the TextChanged event.
But this does not work with my dynamic code.
I have a simple checkbox list and I'm using a for statement to retrieve the selected values into one string. This has to be simple, but everything is returning false when it evaluates if it is selected.
ASP Code
<asp:CheckBoxList runat="server" ID="ckblInterests" ClientIDMode="Static" RepeatColumns="2" />
ASP.NET Code:
string interests = "";
for (int i = 0; i < ckblInterests.Items.Count; i++)
{
if (ckblInterests.Items[i].Selected)
{
interests += ckblInterests.Items[i].Value + ", ";
}
}
}
The inside if statement evaluates as false each time it loops through. It does count 10 items in the list correctly. I'm stumped at something so simple. Can someone help me identify what might be causing the if statement to return false?
You have code that's dynamically adding the checkboxes to the list on page load (or some other event). This is resulting in the state of those checkboxes being cleared and re-added on each postback. Your page load should probably have an if(!page.ispostback) around that section so that you aren't clearing the content.
With the Following Code (Mostly yours)
Aspx
<div>
<asp:CheckBoxList runat="server" ID="ckblInterests" ClientIDMode="Static" RepeatColumns="2">
<asp:ListItem>Awesome</asp:ListItem>
<asp:ListItem>Tasty</asp:ListItem>
<asp:ListItem>Terrible</asp:ListItem>
</asp:CheckBoxList>
</div>
<asp:Button runat="server" ID="test" OnClick="test_Click" />
<asp:Label runat="server" ID="label"></asp:Label>
c#
protected void test_Click(object sender, EventArgs e)
{
string interests = "";
for (int i = 0; i < ckblInterests.Items.Count; i++)
{
if (ckblInterests.Items[i].Selected)
{
interests += ckblInterests.Items[i].Value + ", ";
}
}
this.label.Text = interests;
}
I was able to produce the following. This is of course after clicking the button.
Are you binding to a datasource that you have not mentioned?
make sure while binding the checkboxlist in page load you have set this check if (!Page.IsPostBack) { ...bind your data }
this should do the trick
I think you need to check the CHECKED property, not SELECTED.
I am creating a custom view in a SharePoint visual Web Part using ASP.NET (Visual C#) and have a CheckBoxList, and a button.
MarkUp for the List & Button:
<td>
<asp:checkboxlist ID="cblYearLst" runat="server" EnableViewState="true" />
</td>
<td>
<asp:Button ID="btnRefineSearch" Text="Refine Search" runat="server" />
</td>
I add items to the CheckBoxList on PreRender:
if (!IsPostBack)
{
if (LstYears != null)
{
for (int i = 0; i < LstYears.Count(); i++)
{
cblYearLst.Items.Add(new ListItem(LstYears[i], LstYears[i]));
}
}
}
And I call the event Handler for the button on Page_Load:
btnRefineSearch.Click += new EventHandler(this.btnRefineSearch_Click);
All of the CheckBox list-items do not stay selected after the button is clicked. I can retrieve the selected values, but they won't display as selected. When I add the Click event handler for the button in the pre-render event, the data is displayed appropriately but the selected values can no longer be retrieved by my Click event.
Any ideas on what might be causing this behaviour??
Did you try moving the binding of the checkboxlist into the page_load instead of pre_render? Just an idea because it seems like the page is losing selections on postback and you are regenerating the options each time.
UPDATE: I created a quick page and this works correctly. Do you have your viewstate turned off for the entire page in your page directive, or possibly in the web.config? I see you have it enabled on the checkboxlist but maybe there is a global setting throwing you off.
protected void Page_Load(object sender, EventArgs e)
{
btnRefineSearch.Click += new EventHandler(this.btnRefineSearch_Click);
List<string> LstYears = new List<string>();
LstYears.Add("one");
LstYears.Add("two");
LstYears.Add("three");
LstYears.Add("four");
if (!IsPostBack)
{
if (LstYears != null)
{
for (int i = 0; i < LstYears.Count; i++)
{
cblYearLst.Items.Add(new ListItem(LstYears[i], LstYears[i]));
}
}
}
}
private void btnRefineSearch_Click(object sender, EventArgs args)
{
Response.Write(cblYearLst.SelectedValue);
}
I figured out the issue, since I have AutoEventWireUp set to true as Keenan has suggested it should all work if I do it in the page_load.
The problem was that Page_Load was being called twice, and I discovered that this was because I was redirecting the user to the same URL with QueryString parameters. After I made the much needed changes, my code works very well.
+1 Keenan for your help and thank you (#jfmags) for tipping me off by telling me you think it is something else.
:D
Background
I have a User Control (an .ascx file) which is being dynamically inserting into an asp:PlaceHolder control on a page. That User Control contains an asp:Repeater, which I'm binding to a DataTable.
Theoretically, on the User Control's first load the DataTable is initialized and 3 empty rows are added. A button on the User Control adds additional empty rows to the Repeater, one at a time.
Problem
The issue is that after any PostBack event on the page (namely the button in this example being clicked), the DataTable for the Repeater is empty.
User Control (.ascx)
(simplified)
<asp:TextBox ID="controlOutsideRepeater" runat="server" />
<asp:Repeater ID="myRepeater" runat="server">
<ItemTemplate>
<p><asp:Textbox ID="firstControlInRepeater" runat="server" text='<%# DataBinder.Eval(Container.DataItem, "A") %>' /></p>
<p><asp:Textbox ID="secondControlInRepeater" runat="server" text='<%# DataBinder.Eval(Container.DataItem, "B") %>' /></p>
</ItemTemplate>
</asp:Repeater>
<asp:LinkButton ID="addItemButton" runat="server" Text="Add Item" onclick="addNewItem" />
Code Behind (.ascx.cs)
(also simplified)
public DataTable items {
get {
object i = ViewState["items"];
if (i == null) {
DataTable t = new DataTable();
t.Columns.Add("A");
t.Columns.Add("B");
// add 3 blank items/rows:
t.Rows.Add(t.NewRow());
t.Rows.Add(t.NewRow());
t.Rows.Add(t.NewRow());
ViewState["items"] = t;
return t;
} else {
return (DataTable)i;
}
set { ViewState["items"] = value; }
}
protected void Page_Init(object sender, EventArgs e) {
myRepeater.DataSource = this.items;
myRepeater.DataBind();
}
public void addNewItem(object sender, EventArgs e) {
DataRow r = this.items.NewRow();
this.items.Rows.Add(r);
myRepeater.DataBind();
}
Behavior
The first time the UserControl is loaded, the Repeater contains 3 empty items: good! However, after entering some text in the textboxes both inside and outside the repeater and clicking the "Add Item" LinkButton, the page does a refresh/postback and shows 4 empty items, however the textbox -outside- the Repeater retains it's text. Clicking the "Add Item" LinkButton again also performs a postback and still shows 4 empty items, yet the TextBox outside the Repeater again retains it's text.
My Crazy Guess
I've tried wrapping the Repeater databinding in a (!Page.IsPostBack), but this prevented the Repeater from -ever- being bound, as the UserControl is only programmatically added to the page after a PostBack (a button on the Page adds the UserControl on a click, and then the Page checks each PostBack to see if there should be a user control present and re-adds it to the Page if needed). So I'm guessing there's a problem with the Page re-creating the User Control on every PostBack, but can't explain why the TextBox outside the Repeater would retain it's value, and why the ViewState doesn't seem to remember my item (on each postback ViewState["items"] is null and gets re-built within the getter).
HELP!
The problem is you are data binding every single request when really you only want to data bind on the first request. Since you don't data bind on the first page load, you will have to check if you are data bound in a way other than !Page.IsPostBack. You could add a property to your user control to handle this and then check against that every page load / page init.
Update: With more details from comments
I see your AddItem() now. I've had problems using viewstate this way though I'm not entirely sure why. I've had to do it more like the following:
public void addNewItem(object sender, EventArgs e) {
DataTable theItems = this.items;
DataRow r = theItems.NewRow()
theItems.Rows.Add(r);
this.items = theItems
myRepeater.DataBind(); //I'm not sure if this belongs here because of the reasons said before
}
So I have a country dropdownlist and a state dropdownlist which is being populated dynamically based off of the country chosen. When I click the country the state dropdown gets populated just fine but the problem arises when I click a value (state) from the other dropdown, the list instead of retaining the selected item will go back to the first item of the list and no selectedvalue are displayed.
<td><asp:DropDownList ID="ddlState" runat="server"
DataSourceId="dsStateList"
DataTextField="state_nm"
DataValueField="state_cd"
OnSelectedIndexChanged="ddlState_SelectedIndexChanged"
AutoPostBack="true"
AppendDataBoundItems="true"
Width="160px" OnDataBound="ddlState_OnDataBound">
</asp:DropDownList>
</td>
<asp:DropDownList ID="ddlCountry" runat="server"
DataSourceId="dsCountryList"
DataTextField="COUNTRY_NAME"
DataValueField="COUNTRY_CIA_ID"
OnSelectedIndexChanged="ddlCountry_SelectedIndexChanged"
OnDataBound="ddlCountry_OnDataBound"
AutoPostBack="true"
AppendDataBoundItems="true"
Width="160px">
</asp:DropDownList>
protected void ddlState_SelectedIndexChanged(object sender, EventArgs e)
{
string comboStateCODE = ddlState.SelectedValue;
dsCompanyListParam.Text = comboStateCODE;
ddlCountry.DataBind();
ddlState.DataBind();
}
protected void ddlState_OnDataBound(object sender, EventArgs e)
{
ddlState.Items.Insert(0, "Please Select a State");
}
protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
{
ddlState.Items.Clear();
dsStateList.SelectParameters["iCountryID"].DefaultValue = ddlCountry.SelectedValue;
dsCompanyListParam.Text = ddlCountry.SelectedValue;
Trace.Warn("ddlCountry_SelectedIndexChanged");
ddlCountry.DataBind();
ddlState.DataBind();
}
protected void ddlCountry_OnDataBound(object sender, EventArgs e)
{
ddlCountry.Items.Insert(0, "Please Select a Country");
}
I presume that somewhere in your Page_Load() you are making a call to a method that populates the dropdown... you need to encapsulate this into an IF !PostBack block:
// somewhere in PageLoad()...
If(!IsPostBack)
{
PopulateDropdown();
}
Using the convention above, the dropdown will only be populated on the first ever page load. What I suspect is happening is that when you make a selection from the other dropdown, the AutoPostBack is executing the Page_Load() method (as it should) and repopulating the dropdowns again.
Using the convention above should help avoid this.
Your state drop down is set to Autopostback - is it possible that your code to populate the country drop down is executing again on postback, thus rendering the selected state invalid because the country dropdown was repopulated
I would remove the ddlCountry.DataBind(); from the ddlState_SelectedIndexChanged event. I don't see why you need to do another DataBind there.
Solved it!
Ok, just so anyone who's stuck with a similar problem and can't find any other areas to look at here's how I fixed the stupid problem.
First of all, I was using a stored procedure and the stored procedure is concatenating the values from two fields. I set the parameters the Integer(4) which I didn't noticed there're a couple of countries with codes of more than 4. So basically, it's returning a NULL selectedvalue which in turn will not generate any value since my onselectedindexchanged method is based off of the selectedvalue and for some reason a NULL is not being processed.
So yeah, check your stored procs and parameter data! :D
Thanks for your time!