I have the following DropDownList control:
<asp:label runat="server" text="Filter by state: "></asp:label>
<asp:dropdownlist runat="server" id="filterbystate"
OnSelectedIndexChanged="FilterByState">
<asp:ListItem value="all" selected="True">All</asp:ListItem>
<asp:ListItem value="ca" selected="False">California</asp:ListItem>
<asp:ListItem value="co" selected="False">Colorado</asp:ListItem>
<asp:ListItem value="id" selected="False">Idaho</asp:ListItem>
<asp:ListItem value="ut" selected="False">Utah</asp:ListItem>
</asp:dropdownlist>
Here is the method:
protected void FilterByState(object sender, EventArgs e)
{
var value = e;
}
The method will not fire for some reason. I select a different value and nothing happens. What I am trying to do is reload the page passing in the state value so I can filter the results by it.
What am I doing wrong?
Set AutoPostBack=True as an attribute of your DDL and it will automatically post back the selected index change event
Add this to dropdown list aspx it will cause a request to be send to the server and your event will be fired.
AutoPostBack="true"
You just need to set AutoPostBack = True
From ListControl.AutoPostBack property;
Gets or sets a value indicating whether a postback to the server
automatically occurs when the user changes the list selection.
AutoPostBack="true" and
write page load event
if (!IsPostBack)
{
DDL_Designation_Bind();
}
// Because autopostback properties fire load event then our dropdownlist rebind and always selected index 0 so Not Rebinding dropDownlist
Related
I'm trying to retrieve the value in my dropdownlist that is in my list View.
This is my dropdownlist:
<asp:DropDownList ID="ddlSize" runat="server" CssClass="ddl" AppendDataBoundItems="true" >
<asp:ListItem Value="S">Small +RM5.00</asp:ListItem>
<asp:ListItem Value="M">Medium +RM10.00</asp:ListItem>
<asp:ListItem Value="L">Large +RM15.00</asp:ListItem>
<asp:ListItem Value="X">Xtra-Large +RM20.00</asp:ListItem>
</asp:DropDownList>
This is the current way which I used to retrieve the value of my dropdownlist.
protected void prodList_ItemCommand(object sender, ListViewCommandEventArgs e)
{
size = (e.Item.FindControl("ddlSize") as DropDownList).SelectedValue;
}
By using the method above and got an error Object reference not set to an instance of an object which means im passing a null value.
According to the article, OnItemCommand is only triggered if you have a button inside your ListView Control clicked, are you sure that you had the button already, if yes, I think it should work because I've replicated your issue on my machine?
Article
ASPX FILE contain DropDown as Follows:
< asp:DropDownList ID="drpDist" runat="server" CssClass="dropDownStyle" OnSelectedIndexChanged="drpDist_SelectedIndexChanged" TabIndex="6">
In ASPX.CS FILE
protected void drpDist_SelectedIndexChanged(object sender, EventArgs e)
{
}
Please Help me.I can't get why it is not working.
Use Property
AutoPostBack="True"
you need to set AutoPostBack="true"
<asp:DropDownList ID="drpDist" runat="server" AutoPostBack="true">
when you set that property as true, a postback to the server automatically occurs whenever the user changes the selection of the list
You need to set the AutoPostBack="True" property. This will make the page to postback automatically hence firing your event.
Set AutoPostBack="true"
< asp:DropDownList ID="drpDist" runat="server" AutoPostBack="true" CssClass="dropDownStyle" OnSelectedIndexChanged="drpDist_SelectedIndexChanged" TabIndex="6">
I have an ASP.NET DropDownList control, with a onSelectedIndexChanged event. I also have the AutoPostBack="true" that many have said would fix the problem. However I don't think that is where the problem lays... My Html code and C# code are below for reference. The thing is the code works, but only when I press the enter key while editing the drop down box. If I simply click on an object in the drop down then the event will not fire. If I change the selected item so the "selected" text in the drop down says "ASP" and I then inspect the element using the browser I see that the Selected="True" part of the ListItem is still on the first item... It doesn't change in there. It changes with an enter key but not with a mouse click. Any help is welcome and much appreciated.
HTML:
<div class="ui-widget">
<asp:DropDownList id="Select1" OnSelectedIndexChanged="Select1_SomethingChange" runat="server" AutoPostBack="true">
<asp:ListItem Selected="True" Value="White"> White </asp:ListItem>
<asp:ListItem Value="Select one...">Select one...</asp:ListItem>
<asp:ListItem Value="ActionScript">ActionScript</asp:ListItem>
<asp:ListItem Value="AppleScript">AppleScript</asp:ListItem>
<asp:ListItem Value="Asp">Asp</asp:ListItem>
<asp:ListItem Value="BASIC">BASIC</asp:ListItem>
</asp:DropDownList>
</div>
C#:
protected void Select1_SomethingChange(object sender, EventArgs e)
{
//something is meant to happen here
}
It may be caused by data binding your dropdownlist in Page_Load method.
Please, surround it (data binding) with
if(!IsPostBack){
// data binding.
}
Hope, it help!
AutoPostBack="true"
maybe you miss this option...
Your code works fine, there could be something in code which changes the implementation. I have debug your code and it's showing the selected item in output window. Please verify if there is some javascript code which is causing issue to call dropdown selectedIndexChanged event.
protected void Select1_SomethingChange(object sender, EventArgs e)
{
DropDownList ddl = (DropDownList)sender;
Debug.WriteLine(ddl.SelectedItem.Text);
}
<input runat ="server" type ="checkbox" id="helprequest" />
<label for="helprequest">Help request</label>
<asp:DropDownList ID="options" runat="server" OnSelectedIndexChanged="checkHelpRequest">
<asp:ListItem Text="Windows"></asp:ListItem>
<asp:ListItem Text="Macintosh"></asp:ListItem>
<asp:ListItem Text="Linux"></asp:ListItem>
<asp:ListItem Text="Other"></asp:ListItem>
</asp:DropDownList>
In my codebehind, I have
protected void checkHelpRequest(object sender, EventArgs e)
{
helprequest.Checked = true;
}
But when I select something on the dropdownlist, the checkbox, does not get marked as checked, how do I get the checkbox to appear as checked when I change the index on a dropdownlist?
Your DropDownList does not have AutoPostBack='true' set. Without setting this, your dropdown will not post back when you change the selected index.
Just change it to:
<asp:DropDownList AutoPostBack="true" ID="options"
runat="server" OnSelectedIndexChanged="checkHelpRequest">
Without setting this, your checkHelpRequest method will still be called when your drop down changes index, but only after a postback is caused by some other control, like a button, or another DropDownList that does have AutoPostBack set.
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