I have added the AutoPostBack = "true" attribute to the drop down list.
It doesn't work.
<asp:DropDownList CssClass="dropDownList" ID="ddlBusinessUnit"
AutoPostBack="true" runat="server" Width="250px"
OnSelectedIndexChanged="ddlBusinessUnit_SelectedIndexChanged">
</asp:DropDownList>
code behind:
Protected Sub ddlBusinessUnit_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
Response.Write("Hello")
End
How can I ensure that the event method is called?
Are you populating your Dropdownlist on every Postback?
Use IsPostBack to check whether the page is loaded for the first time or not.
If Not IsPostBack Then
BinDdlBusinessUnit()
End If
Related
So I wanted to make my textbox in asp.net to postback every time a text it typed onto it but i cant seem to figure out how. Does any one knows? here is the code of the event handler
Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtFiltrarNomeUtente.TextChanged
If chkFiltroUtente.Checked And Me.cbxLocal.Text <> "" Then
Me.loadFormInfo()
End If
End Sub
and the textbox
<asp:TextBox ID="txtFiltrarNomeUtente" runat="server" AutoPostBack="true">
so any ideas on how to do it? thanks
You need to add the OnTextChanged event to TextBox txtFiltrarNomeUtente.
<asp:TextBox ID="txtFiltrarNomeUtente" runat="server" AutoPostBack="true" OnTextChanged="TextBox2_TextChanged"></asp:TextBox>
I'm attempting to use Controls.AddAt(), but it apparently breaks controls at later indexes:
Here's my minimal example:
Aspx put in a form:
<asp:DropDownList runat="server" ID="ddl" />
<asp:Button Text="text" runat="server" OnClick="Unnamed2_Click" />
Code Behind:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not IsPostBack Then
ddl.Items.Add("Click the button")
'Controls.Add(New HyperLink) 'Works fine, but is put at end of collection.
'Controls.AddAt(2 ,New HyperLink) 'Is also safe but I wanted the control first
Controls.AddAt(0, New HyperLink) 'ddl loses it's item after postback
End If
End Sub
On the first postback of the page after calling AddAt, the DropDownList loses it's item. It doesn't matter what kind of control I add even HTMLControls. Viewstate is not disabled.
How do I dynamically add controls without breaking others?
If you used a PlaceHolder to add your HyperLink into, it would not mess up the rest of the page:
<asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
<asp:DropDownList ID="ddl" EnableViewState="true" runat="server" />
<asp:Button ID="bn1" Text="text" OnClick="Unnamed2_Click" runat="server" />
With code like
Protected Sub Unnamed2_Click(sender As Object, e As EventArgs) Handles bn1.Click
Dim newItem = "Click the button" & DateTime.Now.ToString("HH:mm:ss")
ddl.Items.Add(newItem)
ddl.SelectedIndex = ddl.Items.Count - 1
PlaceHolder1.Controls.Add(New HyperLink With {.ID = "hyp", .Text = "Hyperlink here"})
End Sub
And always give your asp:Controls an ID if they take one.
I have a simple usercontrol which raises an event on button click
Public Class UcPaymentCheque
Inherits System.Web.UI.UserControl
Public Event OnCancelClick()
Private Sub btnCancelPayment_Click(sender As Object, e As System.EventArgs) Handles btnCancelPayment.Click
RaiseEvent OnCancelClick()
End Sub
End Class
This usercontrol is used within a listview
<asp:ListView ID="lvwNonTpProducts" runat="server" ItemPlaceholderID="ItemPlaceholder">
<LayoutTemplate>
<asp:PlaceHolder ID="ItemPlaceholder" runat="server" />
</LayoutTemplate>
<ItemTemplate>
<TPCustomControl:UcPaymentCheque ID="UcTPPaymentCheque" runat="server" Visible="false" />
</ItemTemplate>
</asp:ListView>
which is databound on page load
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Page.IsPostBack Then
Else
BuildPage()
End If
End Sub
At what point should add the handler? I have fiddled with the ondatabound event like so;
Private Sub lvwNonTpProducts_ItemDataBound(sender As Object, e As System.Web.UI.WebControls.ListViewItemEventArgs) Handles lvwNonTpProducts.ItemDataBound
Dim UcTPPaymentCheque = DirectCast(e.Item.FindControl("UcTPPaymentCheque"), UcPaymentCheque)
AddHandler UcTPPaymentCheque.OnCancelClick, AddressOf OnCancelClick
End Sub
but this does not work and am guess at a databound issue???
You can check out my response to a similar question here: creating and listening for events
Essentially, you want a user control to raise its own event, like this:
Partial Class myControl
Inherits System.Web.UI.UserControl
Public Event MyEvent As EventHandler
'your button click event
Protected Sub bnt_click(ByVal sender As Object, ByVal e As EventArgs)
'do stuff
'now raise the event
RaiseEvent MyEvent (Me, New EventArgs)
end sub
end class
In this example, I raise the event when the user clicks a button within the user control. You can easily raise the event anywhere, such as when the control loads, using a timer, whatever.
Then, in the main page, you want to and an event handler to the user control, like this:
<mc:myControlrunat="server" ID="myControl1" OnMyEvent="myControl_MyEvent" />
Now, in the code behind, you can add the event, like this:
Protected Sub myControl_MyEvent(ByVal sender As Object, ByVal e As EventArgs)
'do stuff
end sub
You can add the handler in the declaration of the user control in the listview, using OnCancelClick, as follows:
<asp:ListView ID="lvwNonTpProducts" runat="server" ItemPlaceholderID="ItemPlaceholder">
<LayoutTemplate>
<asp:PlaceHolder ID="ItemPlaceholder" runat="server" />
</LayoutTemplate>
<ItemTemplate>
<TPCustomControl:UcPaymentCheque ID="UcTPPaymentCheque" runat="server" Visible="false" OnCancelClick="UcTPPaymentCheque_OnCancelClick" />
</ItemTemplate>
</asp:ListView>
Where UcTPPaymentCheque_OnCancelClick is the function you should use to handle the event, in the control that contains the listview.
Ok I am using a column with check box to be able to select my data row from a GridView. But The OnCheckChanged event won't fire. I have tried reading articles to make it work and copy code exactly and it just won't fire. I am using vb.net and asp.net
<asp:GridView ID="locationDetailGrid" runat="server">
<Columns>
<asp:TemplateField>
<ItemTemplate >
<asp:CheckBox ID="locationSelection" AutoPostBack="true"
runat="server" OnCheckedChanged="CheckedChanged" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Protected Sub CheckedChanged(ByVal sender As Object, ByVal e As EventArgs)
Dim checkbox As CheckBox = DirectCast(sender, CheckBox)
Dim row As GridViewRow = DirectCast(checkbox.NamingContainer, GridViewRow)
Response.Write(row.Cells(0).Text)
End Sub
Probably because you're databinding the GridView also on postbacks. Add an If Not Page.IsPostback into Page_Load around your databinding stuff of the GridView.
If you rebind the GridView on postbacks, you're preventing events from triggering.
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not IsPostBack Then
BindGridToDataSourceAndDataBind()
End If
End Sub
I am experiencing a problem with buttons and AddHandler. It only works if I use AddHandler Button1.click, AddressOf... in Page_load, but if I create the button dynamically in one of the sub routines, the event doesn't fire.
For example,
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True">
<asp:ListItem>1</asp:ListItem>
<asp:ListItem>2</asp:ListItem>
</asp:DropDownList>
<asp:ScriptManager id="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:UpdatePanel id="UpdatePanel1" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="False">
<contenttemplate>
<asp:PlaceHolder id="PlaceHolder1" runat="server"></asp:PlaceHolder>
</contenttemplate>
</asp:UpdatePanel>
<asp:UpdatePanel id="UpdatePanel2" runat="server" UpdateMode="Conditional">
<contenttemplate>
<asp:Label id="Label2" runat="server" Text="Label"></asp:Label>
</contenttemplate>
</asp:UpdatePanel>
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
Label1.Text = Date.Now
ScriptManager1.RegisterAsyncPostBackControl(DropDownList1)
End Sub
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
Label2.Text = "Panel refreshed at " + Date.Now.ToString()
End Sub
Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
Dim b As New Button
b.Text = "Click"
ScriptManager1.RegisterAsyncPostBackControl(b)
AddHandler b.Click, AddressOf Button1_Click
PlaceHolder1.Controls.Add(b)
UpdatePanel1.Update()
End Sub
The dropdownlist works, but the button doesn't. What am I doing wrong?
You have to regenerate your dynamically created controls on every postback (at last in Page_Load, better in Page_Init). You have to set the ID of the controls accordingly because ASP.Net needs it to identify which control caused a Postback and to handle the appropriate events.
You could save the number of created buttons in ViewState and use this to regenerate them on Page_Load. Increase the number when you add a new button. Use this number also to make the Button's ID unique(append it to the ID) to ensure that its the same on every postback.
For further informations, have a look the Page-Lifecycle and ViewState with dynamically added controls.
Edit: As Joel commented, if you only need one Button you can set it's ID statically, but you have to regenerate it on postback f.e. to handle its click-event.
Just to aid anyone who has this problem and isn't quite sure how to implement. Here's a quick example.
This example starts out by displaying a dropdownlist. When user selects something from the dropdown, another dropdownlist appears.
I typed this off the top of my head, so it MAY contain errors, but you get the idea =)
In the aspx file, add a placeholder:
And in your codebehind:
...
Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
'Store control count in viewstate
If Not IsPostBack Then ViewState("ControlCounter") = 1
'Rebuild dynamic controls on every postback so when page's life cycle hits Page_Load,
'selected values in the viewstate (asp.net default behavior) can be loaded into the dropdowns
Build_Dynamic_Controls()
End Sub
Protected Sub Build_Dynamic_Controls()
'Clear placeholder
myPlaceholder.Controls.Clear()
'This is where the control counter stored in the viewstate comes into play
For i as Integer = 0 To CInt(ViewState("ControlCounter") -1
Dim ddlDynamic as New DropDownList With {
.ID = "ddlDynamicDropdown" & i,
.AutoPostBack = True
}
'This is the event that will be executed when the user changes a value on the form
'and the postback occurs
AddHandler ddlDynamic.SelectedIndexChanged, AddressOf ddlDynamic_SelectedIndexChanged
'Add control to the placeholder
myPlaceholder.Controls.Add(ddl)
'Put some values into the dropdown
ddlDynamic.Items.Add("Value1")
ddlDynamic.Items.Add("Value2")
ddlDynamic.Items.Add("Value3")
Next i
End Sub
Protected Sub ddlDynamic_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
'When a dropdown value is changed, a postback is triggered (autopostback=true)
'The event is captured here and we add another dropdown.
'First we up the control count:
ViewState("ControlCounter") = CInt(ViewState("ControlCounter")) + 1
'Now that the "total controls counter" is upped by one,
'Let's recreate the controls in the placeholder to include the new dropdown
Build_Dynamic_Controls()
End Sub
...