I am trying to setup a cascaded drop down box where the first one will result in the second one's value being changes and so on. I have some markup like this:
<form id="ddlSelections" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true" />
<asp:UpdatePanel ID="UpdatePanel2" runat="server" ChildrenAsTriggers="true" UpdateMode="Conditional">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="DDL1" EventName="SelectedIndexChanged" />
<asp:AsyncPostBackTrigger ControlID="DDL2" EventName="SelectedIndexChanged" />
</Triggers>
<ContentTemplate>
<asp:DropDownList ID="DDL1" OnSelectedIndexChanged="OnDDL1Change" AutoPostBack="true" runat="server" />
<asp:DropDownList ID="DDL2" OnSelectedIndexChanged="OnDDL2Change" AutoPostBack="true" runat="server" />
<asp:DropDownList ID="DDL3" runat="server" />
</ContentTemplate>
</asp:UpdatePanel>
</form>
And my code-behind is something like this:
protected void Page_Load(object sender, EventArgs e)
{
populateDDL1();
}
private void populateDDL1()
{
DDL1.Items.Clear();
// -- populate from SQL
}
protected void OnDDL1Change(object sender, EventArgs e)
{
DDL2.Items.Clear();
// -- populate from SQL
}
This is working except that everytime I click on the first drop down box, the values in the second drop down box get populated but the values in the first drop down box are being re-populated i.e. it looks like populateDDL1() is being called which of course will not be called unless Page_Load is called! I am failing to understand why this is the case. Any suggestions on where I am going wrong?
You are populating the first dropdownlist on every page load.
You need to do that only on the first load.
Wrap your populateDDL1 call in if (!IsPostBack), which is a backward way of saying to only populate it the first time the page loads.
To test this, put a breakpoint on that line in Page_Load.
Just because it's an ajax-y UpdatePanel doesn't mean that the server-side methods don't run.
Related
Situation:
Checkbox inside a updatepanel
multiline textbox inside a different updatepanel.
if the user checks the checkbox, the multiline text box gets a name... this works fine.
HTML:
<asp:UpdatePanel ID="upTraveling" runat="server"
UpdateMode="Conditional" ChildrenAsTriggers="False">
<ContentTemplate>
<asp:CheckBox ID="cbRUTraveler" runat="server" Text="I am a Traveler" AutoPostBack="True"
oncheckedchanged="cbRUTraveler_CheckedChanged1" />
</ContentTemplate>
</asp:UpdatePanel>
<td>
<asp:UpdatePanel ID="upTravelers" runat="server" ondatabinding="cbRUTraveler_CheckedChanged1"
UpdateMode="Conditional">
<ContentTemplate>
<asp:TextBox ID="tbTravelers"
Class="textwidth" runat="server" TextMode="MultiLine"
placeholder="FName LName, FName LName" required="required">
</asp:TextBox>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger
ControlID="cbRUTraveler" EventName="CheckedChanged" />
</Triggers>
</asp:UpdatePanel>
C#:
protected void cbRUTraveler_CheckedChanged1(object sender, EventArgs e)
{
tbTravelers.Text =
RequesterBPL.RequesterTraveling(cbRUTraveler.Checked, tbTravelers.Text);
going = cbRUTraveler.Checked;
}
I also have 2 other updatepanels on the same page... a dropdown list in one updatepanel and a label in another updatepanel. When a user selects a value in the dropdown list... it's suppose to trigger a name placement in the label.
HTML:
<td>
<asp:UpdatePanel ID="upManager" runat="server"
ondatabinding="ddlTeam_SelectedIndexChanged"
UpdateMode="Conditional">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="ddlTeam"
EventName="SelectedIndexChanged" />
</Triggers>
<ContentTemplate>
<asp:Label ID="lblManager" runat="server" > </asp:Label>
</ContentTemplate>
</asp:UpdatePanel>
</td>
C#:
protected void ddlTeam_SelectedIndexChanged(object sender, EventArgs e)
{
//upManager.Update();
lblManager.Text =
ManagerBPL.ReturnManagerName(ddlTeam.SelectedIndex);
}
However, when a user makes a selection in the dropdown, nothing happens.
until the user checks the checkbox which has nothing to do with the label and the dropdown. Once the user checks (or unchecks) the checkbox... the label gets populated with the selection from the dropdown.
All controls are in a table for structure. I have the scriptmanager in place.
From what I've been reading on the net this maybe a bug... If not a bug does anyone see where I may be going wrong...?
Thanks
Honestly you could do this all Client-Side. A simple example:
$(function () {
$('#<%= drpContent.ClientID %>').blur(function () {
var content = $('#<%= drpContent.ClientID %> option:selected').val();
$('#lblContent').text(content);
}
});
I've provided the initial example with the value declared. The second example is with a text representation.
$(function () {
$('#<%= drpContent.ClientID %>').blur(function () {
var content = $('#<%= drpContent.ClientID %> option:selected').text();
$('#lblContent').text(content);
}
});
An example with a Fiddle. The example though is simple, is far easier then dealing with an Update Panel. That particular control can be a nightmare to deal with, it can be quite painful. Though you asked about the server issue, this option is more viable and more common.
Update Panel (Drawback):
Creates pandomonium between Client / Server Side Events.
Stores your entire page in memory, then recreates (Performance Heavy)
Often breaks Page-State quickly in the Asp.Net Page Life Cycle.
Hopefully this helps.
All I wish to do is simply click a button and the text in a textbox is automatically added as an item in the listbox. Shouldn't this be straight forward? Whilst debugging, the item is added and I can see the text by watching ListBox1.Items[0], but nothing is displayed in the web page. I had the same problem which i did not solve, in a console application! Can some one please guide me to what I am doing wrong?
protected void Button1_Click(object sender, EventArgs e)
{
ListBox1.Items.Add(new ListItem(TextBox1.Text));
}
Many thanks
Edit:
In a past project, I used the DataSource property, which worked perfectly. I have never yet managed to use the add Items! May be there is some sort of refresh or update?
Page code:
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:ListBox ID="ListBox1" runat="server" Height="150px" Width="295px"></asp:ListBox>
<asp:UpdatePanel ID="updatePanel1" runat="server">
<ContentTemplate>
<asp:Button ID="Button1" runat="server" Text="Submit" OnClick="Button1_Click" />
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</ContentTemplate>
</asp:UpdatePanel>
Looks like your listbox is outside of the update panel. Pop it inside the update panel:
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:DropDownList ID="DropDownList1" runat="server">
</asp:DropDownList>
<asp:Button ID="Button1" runat="server" Text="Button" onclick="AddItem" />
</ContentTemplate>
</asp:UpdatePanel>
You have to move the ListBox into the UpdatePanel, otherwise it will not be updated.
The reason for that is, that ASP.NET is sending the whole HTML of the UpdatePanel back to the client. Since the ListBox is not part of the UpdatePanel, it won't be updated.
I have two radio buttons both set as async triggers for an update panel and problem is that first time one is clicked the CheckedChanged event fires but then no matter which radio button is clicked the event never fires again.
Markup:
<asp:RadioButton ID="rdoDeliveryBilling" runat="server" Checked="true" GroupName="DeliveryAddress" Text="Deliver to this address" AutoPostBack="true" OnCheckedChanged="rdoDelivery_CheckedChanged" />
<asp:RadioButton ID="rdoDeliveryShipping" runat="server" GroupName="DeliveryAddress" Text="Deliver to a different address" AutoPostBack="true" OnCheckedChanged="rdoDelivery_CheckedChanged" />
<asp:UpdatePanel ID="panDeliveryAddress" runat="server">
<ContentTemplate>
...delivery details form controls and validators goes here...
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="rdoDeliveryBilling" EventName="CheckedChanged" />
<asp:AsyncPostBackTrigger ControlID="rdoDeliveryShipping" EventName="CheckedChanged" />
</Triggers>
</asp:UpdatePanel>
Code:
protected void rdoDelivery_CheckedChanged(object sender, EventArgs e)
{
...only code that enables/disables the delivery form controls and validators goes here...
}
I have set a breakpoint inside rdoDelivery_CheckedChanged and it only hits the first time.
Any ideas?
Looking at the source (in the browser), ASP.NET is only generating a post back function __doPostBack for the RadioButton controls which can possibly postback.
The first RadioButton control cannot postback (because it is already checked), and as such the __doPostBack is not generated.
A work around is to add the two RadioButton controls to another UpdatePanel, setting the UpdateMode to Always. This will cause the RadioButtons to be updated (whenever they trigger the other UpdatePanel) adding the __doPostBack function to the deselected RadioButton.
Example
<asp:UpdatePanel ID="UpdatePanelCheckBoxes" runat="server" UpdateMode="Always">
<ContentTemplate>
<asp:RadioButton ID="rdoDeliveryBilling" runat="server" Checked="true" GroupName="DeliveryAddress" Text="Deliver to this address" AutoPostBack="true" OnCheckedChanged="rdoDelivery_CheckedChanged" />
<asp:RadioButton ID="rdoDeliveryShipping" runat="server" GroupName="DeliveryAddress" Text="Deliver to a different address" AutoPostBack="true" OnCheckedChanged="rdoDelivery_CheckedChanged" />
</ContentTemplate>
</asp:UpdatePanel>
Hope this helps.
I have an Update panel within a wizard:
<asp:WizardStep ID="WizardStep2" runat="server" StepType="Auto"
Title="Set the number of users required.">
...
<asp:UpdatePanel ID="UpdatePanel2" UpdateMode="Always" runat="server">
<ContentTemplate>
<asp:Label runat="server" ID="ProgressInd" Text="Progress..." />
<asp:Button runat="server" OnClick="GoButton_Click" ID="ProgressBtn" Text="Go" />
</ContentTemplate>
</asp:UpdatePanel>
</asp:WizardStep>
...
protected void GoButton_Click(object sender, EventArgs e)
{
ProgressInd.Text = "Progress... Moving";
}
When I take the update panel out of the wizard it works nicely but inside the wizard the click event just won't fire. I'm using Firefox to test, but IE doesn't work either. Any ideas or help appreciated.
For the record. Paolo spotted my problem. There were page validators that were preventing the event from firing.
I use UpdatePanel with DataList element inside. I want to update the contents from DB every 10 secunds. I noticed that updating occures only after the postback. I did the code like
<asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Conditional" runat="server">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Timer1" EventName="Tick" />
</Triggers>
<ContentTemplate>
<asp:DataList ID="lstComputers" runat="server" DataKeyField="ComputerID" DataSourceID="ComputersDataSource"
OnItemDataBound="lstComputers_ItemDataBound" OnItemCommand="lstComputers_ItemCommand">
<HeaderTemplate>
// Header data
</HeaderTemplate>
<ItemTemplate>
// Item template
</ItemTemplate>
</asp:DataList>
<asp:UpdateProgress ID="UpdateProgress2" runat="server">
<ProgressTemplate>
<img border="0" src="images/loading.gif" />
</ProgressTemplate>
</asp:UpdateProgress>
</ContentTemplate>
</asp:UpdatePanel>
In code behind i tryed to use RaisePostBackEvent method but got Stack overflow exception...
protected void Timer1_Tick(object sender, EventArgs e)
{
this.RaisePostBackEvent(Timer1, "");
}
Remember that all your code-behind is executed on the server only. Therefore, if the Timer1_Tick() method is running, then your Timer is raising a PostBack.
The reason you get a StackOverflowException running that method is because it simply calls itself, infinitely. You need to place your update code in that method, not call it again recursively.
Take a look at the setTimeout() and setInterval() javascript functions. This all needs to happen on the client, not the server side.
protected void Timer1_Tick(object sender, EventArgs e)
{
lstComputers.DataBind();
}
Solved the problem with data reloading