I have a non-databound Dropdownlist inside of an UpdatePanel:
<asp:UpdatePanel runat="server" ID="FiltersUpdPnl">
<ContentTemplate>
<div class="filters">
<asp:Button runat="server" ID="ExportBtn" Text="Export Map to Image" />
<br />
Show:
<asp:DropDownList runat="server" ID="CapNumProjectsDDL" AutoPostBack="true" OnSelectedIndexChanged="ApplyFilters" OnPreRender="CapNumProjectsDDL_PreRender">
<%--<asp:ListItem Value="0" Text="" Selected="True"></asp:ListItem>--%>
<asp:ListItem Value="1" Text="Capacity"></asp:ListItem>
<asp:ListItem Value="2" Text="Number of Projects"></asp:ListItem>
</asp:DropDownList>
</div>
</ContentTemplate>
</asp:UpdatePanel>
The event handler isn't terribly important, it just does stuff:
protected void ApplyFilters(object sender, EventArgs e)
{
//Do Stuff relating to the selected Value
}
When the page loads, "Capacity" is selected by default, as it's the first ListItem. When I switch off to "Number of Projects", the event handler fires as expected, executing the code. But when I switch back to "Capacity", the handler does NOT fire. The Postback is occurring, but I want it to specifically hit the event handler on both listitems.
You can see that I have a commented-out "0-value" ListItem in there. When I uncomment that, both "Capacity" and "Number of Projects" will hit the event handler as expected.
The issue is that when the page loads, it's loading the data relevant to the "Capacity" dropdown, so I want the "Capacity" ListItem to be showing, but be able to fire the event handler when selected.
Am I missing something obvious here?
E: I tried adding a handler for the DDL_Prerender event, setting the SelectedIndex to like 200 or something clearly not in the list, hoping it would de-select "Capacity", but that didn't work either.
This is the Pre-render code:
protected void CapNumProjectsDDL_PreRender(object sender, EventArgs e)
{
CapNumProjectsDDL.SelectedIndex = 200;
}
This didn't change the way it worked.
It seems that you want that drop down element raise change even if you select in drop down box already selected item. I believe that this will not work, and the cause of the problem is not in server side asp.net dropdownlist control, but in how HTML select element is working to which DropDownList control is rendered.
The problem is that HTML select element doesn't fire change event if user select the same item as was before drop box was shown (because from the point of view of control state - it was not changed).
So, I believe that the behavior that you want can be implement, but you should not use HTML select control and instead of it implement custom solution.
Related
I have a control and Event Handler:
<asp:DropDownList ID="SortDirection1" runat="server"
OnSelectedIndexChanged="SortDirection_SelectedIndexChanged"
AutoPostBack="true">
<asp:ListItem Selected="True" Value="0"> ASC </asp:ListItem>
<asp:ListItem Value="1"> DESC </asp:ListItem>
</asp:DropDownList>
and
protected void SortDirection_SelectedIndexChanged(object sender, EventArgs e)
{
var DDL = (sender as DropDownList);
Session["SortDirection"] = DDL.SelectedIndex;
}
If I change selection in DropDownList, page will be reloaded and only after it this handler will be triggered. So, there is a problem. I try to use Session["SortDirection"] before it will be rewrited. The question is How to rewrite Session["SortDirection"] before page reloading?
You are using an autopostback on the DDL and then setting a session value in the Selected Index Changed event. The correct place to use that value is in the Load Complete event. That event gets fired after the Selected Index Change event.
It is very beneficial to learn the complete ASP.NET page lifecycle. There is a nice diagram in the "Additional Page Life Cycle Considerations" section that shows the events and methods for the page and its controls. The Selected Index Change event happens in Event Handling section.
The Load Complete happens after that. This gets raised when all of the process has been completed and just before the rendering starts. The purpose of the Load Complete is to give you a place for logic once all of the setup and processing is finished.
I am using CreateUserWizard and added additional WizardStep for user additional details.
I am using one dropdownlist. value has been filled from DB in dropdownlist.
Now, when I will change the value in dropdownlist. I want to chekc/uncheck the one checkbox based on it's value in DB for selected dropdownlist value.
For that i want to call onselectedindexchanged event of dropdownlist.
How to fire onselectedindexchanged event?
Please help me to solve this problem?
Dont add onselectedindexchanged manually
All event for element are listed in event tab on right hand side
Your code should look like
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"
onselectedindexchanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>
In cs file
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
}
Important Note
Remove the ViewStateMode="Disabled" in the CreateUserWizard control
Try this.
drag a dropdownlist control on your aspx page and add selectedindexchanged event, test it properly, now cut the control and paste it inside WizardStep.
I hope it works.
I have two asp:Labels, the first of which is replaced with a few buttons and the second with a list of items.
I want to click on the buttons to filter the items.
The contents of the buttons are added programmatically by replacing the text with html and works fine.
asp:
<form id="form1" runat="server">
<asp:Label id="filters" runat="server" Text="Filters here"/>
<asp:Label id="itemList" runat="server" Text="List of items here"/>
</form>
resultant html of filters label:
<input type="submit" onclientclick="Load_Items(0)" runat="server" value="First"/>
<input type="submit" onclientclick="Load_Items(1)" runat="server" value="Second"/>
<input type="submit" onclientclick="Load_Items(2)" runat="server" value="Third"/>
relevant c#:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Load_Items(0);
}
}
public void Load_Items(int filterType)
{
//code to load items (pseudo below)
for each row in list
if filterType = itemType
build string
replace second label with string
}
On page load everything happens just as I want it to with the contents being filtered by the first item (hence Load_Items(0)), and if I manually change the 0 to another number in Page_Load, it filters by the other types, but if I click the buttons which are programmatically added, nothing happens other than what looks like the page refreshing.
I know the post back check is working by adding a text replacement before and inside it.
I've also added an asp:button to make sure it's not something to do with the way the buttons are added as below (with some extra things recommended from searches):
<asp:Button runat="server" CausesValidation="False" onclientclick="Load_Items(2); return false;" text="Submit" />
So what could be the issue?
The OnClientClick property specifies the javascript to run in the browser when the button is clicked. Since you probably don't have a javascript function called Load_Items, this will generate a script error, and the button will then cause the form to post back.
The server-side Click event will fire on the server, but doesn't allow you to pass a parameter. You will only get the button instance and an empty EventArgs instance.
You might be better off using the Command event, combined with the CommandArgument property.
<asp:Button runat="server" CommandArgument="2" OnCommand="Load_Items" ...
The event handler would use the CommandArgument property of the CommandEventArgs to access the argument from the clicked button:
protected void Load_Items(object sender, CommandEventArgs e)
{
Load_Items(Convert.ToInt32(e.CommandArgument));
}
Well, that's the common problem which I think every asp.net developer deals some time. The common part of it, that asp.net event system doesn't work, as windows forms.
Page object, and all controls on that page, have lifecycle events, that are triggered during any request, even when it's from update panel.
As you create those controls by code, you have to keep in mind, that all events for those controls should work as part of Page object. That's why you have to create those object in Page_Init event, before all other control's event would be triggered.
Please also keep in mind that you have to create those controls as asp.net objects:
var btn = new Button();
But not by simply adding html markup. And you have to recreate them on each request, following that one, when they were created.
Please take a look on my another answer.
Evening all
I have the following scenarion. I have a range of drop down menus where a clietn can select. The code below is wrapped in an update panel but without this, the button click fires a method to retrieve the number of products. So for example, an item is selected from ddlCategory, the btnValidate is clicked and the label returns the number of products within that category.
I have the following code for an update panel - I'm just not sure how to implement if effectively.
<asp:UpdatePanel ID="UpdatePanel1" runat="Server">
<ContentTemplate>
<asp:Label ID="lblSearchResultsStatus" runat="server" Text="Number of results found: "></asp:Label>
<asp:Label ID="lblSearchResults1" runat="server" Text=""></asp:Label>
<br />
<br />
<asp:Button ID="btnValidate" runat="server" Text="Validate Search"
OnClick="btnValidate_Click" Width="120px" />
</ContentTemplate>
</asp:UpdatePanel>
How do I go about wiring the update panel so that when a drop down list item is selected, the buttong is effectively clicked?
Do I have to implement something on each of the ddlSelectedIndexChanged event or is there a property within the update panel that does?
Apologies for the noob question.
The point of the UpdatePanel is to update a portion of the page with an AsyncPostBack instead of reloading the whole page, but in order for the drop-down lists to trigger an AsyncPostBack automatically, they must be on an UpdatePanel. In order to update the labels, they must be on the same UpdatePanel with the labels.
A common pattern to implement what you want to accomplish:
Put the DDLs on the UpdatePanel, and set AutoPostBack="true" on each DDL, so they trigger AsyncPostBacks.
Add an event handler for SelectedIndexChanged on each DDL (can be the same event handler).
Move whatever you do in btnValidate_Click to another method.
Call the new method from btnValidate_Click and the SelectedIndexChanged event handler(s) so they all perform the same function.
You can call your btnValidate_Click event from codebehind at any point, i.e. Page_Load
protected void Page_Load(object sender, EventArgs e)
{
btnValidate_Click(btnValidate, new EventArgs());
}
I am looking into using only a ddl to run my query, not a ddl and a Button_Click function. I am yet to find what to do. How do I do this?
In your as(p/c)x:
<asp:DropDownList runat="server"
id="ddl"
OnSelectedIndexChanged="SelectionChanged"
AutoPostBack="true">
<asp:ListItem Text="Page 1" Value="/page1.aspx" />
<asp:ListItem Text="Page 2" Value="/page2.aspx" />
</asp:DropDownList>
The "AutoPostBack" property tells ASP.NET to wire up a client-side (javascript) command that submits the form as soon as the drop down list changes, instead of waiting for a button click.
And in your codebehind, the event handler we referenced in the "OnSelectedIndexChanged" property will get fired:
protected void SelectionChanged(object sender, EventArgs e)
{
Response.Redirect(((DropDownList)sender).SelectedValue);
}
Set the AutoPostBack property to true, then hook into the OnSelectedIndexChanged event
<asp:DropDownList
id="dropDownList1"
runat="server"
AutoPostBack="true"
OnSelectedIndexChanged="dropDownList1_SelectedIndexChanged" />
Server Side
void dropDownList1_SelectedIndexChanged
(Object sender, EventArgs e) {
//run your query
}
Ensure your Drop down list has it's "AutoPostback" property set to true. This will cause the page to post back when the user selects an item from within the drop-down list. You can respond to this in your code-behind in whichever event you desire, Page_Load, or the DDL's own OnSelectedIndexChanged