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);
}
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
I have a code like this:
on.aspx page
<asp:ListItem Value="1"> 1</asp:ListItem>
<asp:ListItem Value="2"> 2</asp:ListItem>
<asp:ListItem Value="2" Selected="True"> 3</asp:ListItem>
<asp:ListItem Value="4"> 1</asp:ListItem>
</asp:DropDownList>
<br />
<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
on aspx.cs page
protected void Page_Load(object sender, EventArgs e)
{
//do something
}
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
}
protected void Button1_Click(object sender, EventArgs e)
{
}
here issue is that, when i click on button at that time DropDownList1_SelectedIndexChanged also firing.
as i gone thru and found that this happening due to same value for different itemtext.
<asp:ListItem Value="2"> 2</asp:ListItem>
<asp:ListItem Value="2" Selected="True"> 3</asp:ListItem>
I can`t do changes in value.
Is there any luck? or what the exactly issue is?
Thanks,
Vijay
Please check DropDownList AutoPostBack Property.
if AutoPostBack is true
Gets or sets a value indicating whether a postback to the server
automatically occurs when the user changes the list selection.
SelectedIndexChanged fires when the selection changes. It does not take into account the values or text being the same.
That is why it is named SelectedIndexChanged & not SelecteValueChanged OR SelectedTextChanged.
So if you want your SelectedIndexChanged event and also want that it does not fire if it has the same Value or Text. It would not be possible.
IMHO : Value OR Text should not be duplicated in a DropDownList. You should get rid of the duplicate values from the DataSource before binding it.
Make sure ViewState is Enabled on Web Page and add it on Page load
if (!IsPostBack)
{
//do code here
}
So i have this checkbox list and im trying to generate a textbox when the MISC checkbox is checked.
<asp:CheckBoxList ID="chbxEquipmnt" runat="server"RepeatColumns="4" RepeatDirection="Horizontal" ValidationGroup="Equipment" OnSelectedIndexChanged="chbxEquipmnt_SelectedIndexChanged">
<asp:ListItem Value="Laptop">Laptop</asp:ListItem>
<asp:ListItem Value=" Label Printer">Label Printer</asp:ListItem>
<asp:ListItem Value="Printer">Printer</asp:ListItem>
<asp:ListItem Value="Fax Line">Fax Line</asp:ListItem>
<asp:ListItem Value="PC">PC</asp:ListItem>
<asp:ListItem Value="MFD">MFD</asp:ListItem>
<asp:ListItem Value="Phone Line">Phone Line</asp:ListItem>
<asp:ListItem Value="Misc">Misc</asp:ListItem>
</asp:CheckBoxList>
ON my Cs page I have.........
protected void chbxEquipmnt_SelectedIndexChanged(object sender, EventArgs e)
{
if (chbxEquipmnt.SelectedValue == "Misc")
{
TextBox txt = new TextBox();
txt.ID = "txtMiscCheckBox";
Page.Form.Controls.Add(txt);
}
}
debugging i have tried with Postback which continuously on returns the first check box that was checked...for example i checked laptop instead of Misc first, the value in the debugger always show me laptop. Im not sure if a simple loop to go thru the all the button clicks would help.....I'm fresh out of school and this is a career change for me so thanks for the patience
I would change the approach: don't create the Textbox at run time.
Have it created at design time, hide it by default (Visible property), then show it when Misc option is selected.
You will run into less issues that way. Creating controls in runtime require some extra effort : dealing with ViewState, re-creating the control on PostBack, etc.
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
<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.