I have a button that is created after a user selects a certain value from a dropdown menu, but it is not firing its' EventHandler. Is there something with the Lifecycle, OnInit possibly, that I have to refresh for the handler to fire correctly?
Event fired from DropDownList's OnSelectedIndexChanged
protected void Selected_floor_first(object sender, EventArgs e)
{
Button btn = new Button();
btn.ID = "room_button_1";
btn.Text = "Select";
btn.Click += new EventHandler(room_1_Click);
floor_1_room_overlay.Controls.Add(btn);
}
Handler: (Not Firing)
protected void room_1_Click(object sender, EventArgs e)
{
validation.Text = "You selected a Room";
}
If you must create your button dynamically, create it inside the OnInit() method of the page.
Event handling happens after Page Init. So, the button will have to be created before Page Init, for the events to be handled.
As it is dynamically added, you have to take that code in Page_Init() event that occurs after every postback. otherwise when the postback occurs, there is no room_button_1 in the forms.controls collection and the event is missed. So
add it as it is being added.
after adding set a variable in session to identify that dynamic control has been added
on page_init() check the session variable of step2. if it says yes then create the control you created in step 1.
Instead of repeating the code, it's better if you create a function for button creation and call it from your Select_floor_first() and Page_Init().
The button goes out of scope mate. define it as a private variable otherwise the event wont fire as the button disposed after Selected_floor_first method finishes
private Button btn = new Button();
protected void Selected_floor_first(object sender, EventArgs e)
{
btn.ID = "room_button_1";
btn.Text = "Select";
btn.Click += new EventHandler(room_1_Click);
floor_1_room_overlay.Controls.Add(btn);
}
protected void room_1_Click(object sender, EventArgs e)
{
validation.Text = "You selected a Room";
}
Related
I have created button manually from the behind code page using asp.net WebForms.
That is the creation code:
Button myButton = new Button();
myButton.ID = "b" + arrcodes[i];
myButton.Text = "Buy Now!";
myButton.CssClass = "btn-primary";
myButton.Click += new EventHandler(myButton_Click);
myPlaceHolder.Controls.Add(myButton);
I googled how to add onClick function and used method which founded here in stackoverflow. But this method not working.. the function "myButton_Click" isnt activated when i press the button.
protected void myButton_Click(object sender, EventArgs e)
{ // my code }
Have i did something wrong?
You will need to reload that dynamically created button on postback with same Id inside Page_Init or Page_Load event.
Otherwise, it won't be in the Control Tree, and cannot trigger the Click event.
For example,
public partial class Default : System.Web.UI.Page
{
protected void Page_Init()
{
CreateButton();
}
protected void myButton_Click(object sender, EventArgs e)
{
}
private void CreateButton()
{
Button myButton = new Button();
myButton.ID = "b1";
myButton.Text = "Buy Now!";
myButton.CssClass = "btn-primary";
myButton.Click += new EventHandler(myButton_Click);
myPlaceHolder.Controls.Add(myButton);
}
}
Usually, the better option is to create the button and toggle it's visibility.
If you really need to create it dynamically, make sure you're creating the button in OnInit method for event handler to work.
Some context. I've added inside Page_Load of a class Method1 that generates a repeater and Method2 that generates an array of buttons.
Each button is attached dynamically an event inside Method2.
The buttons will never change, but based on clicking a button the repeated elements should change.
My main problem is/are:
1) when I click a button, the event causes the page to load (Page_Load) which calls Method1, which generates the default repeater, instead of the one associated with my specific event attached to button x from the array of buttons; --> so, I wrapped up Method1 in !isPostBack ... then, nothing happens at all
How would you avoid this? What principles would you use for implementig this?
Attempted so far:
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
GetItems(1, 2); //default values (first time the page is loaded)
GenerateButtons(10);
}
}
private void GenerateButtons(int c)
{
LinkButton[] x = new LinkButton[c];
for(int i=0; i<c;i++)
{
x[i] = new LinkButton();
x[i].Text = (i+1).ToString();
Panel1.Controls.Add(x[i]);
x[i].OnClientClick += new EventHandler(Button_Click);
}
}
protected void Button_Click(object sender, EventArgs e)
{
Button button = (Button)sender; // Which button was clicked;
GetItems(int.Parse(button.Text)-1, 3); //3 is a constant; first argument is index of button extracted from its caption
}
//clicking a button should load the page invoking GetItems() specific to the button pressed (first argument is its index) and should regenerate the buttons, maybe highlighting in some way the one that was previously pressed.
To help performance, it would also help not to regenerate the buttons after a page was first loaded.
I'm working with ASP.NET and C#.
My main problem is Button_Click is never invoked, probably because the buttons are regenerated when clicking a button so their definitions is recreated, including the buttons' events.
Your Button_Click handler would always be fired before the regeneration, anyway; so this is not the problem.
Your problem, however, lies in your x[i].OnClientClick += ... code.
You need to hook up to the .Click event of the LinkButton to listen to the right event.
Like this:
private void GenerateButtons(int c)
{
LinkButton[] x = new LinkButton[c];
for(int i=0; i<c;i++)
{
x[i] = new LinkButton();
x[i].Text = (i+1).ToString();
Panel1.Controls.Add(x[i]);
x[i].Click += new EventHandler(Button_Click); // Use the 'Click' event
}
}
Hope this helps!
I am trying to call dynamically created button click event. I this event I want to show one message on clicking dynamically created button.
my Code
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnMain_Click(object sender, EventArgs e)
{
Button btnNew = new Button();
btnNew.ID = "btnClick";
btnNew.Text = "Click";
btnNew.Click += new System.EventHandler(btnNew_Click);
this.form1.Controls.Add(btnNew);
}
protected void btnNew_Click(object sender, EventArgs e)
{
Label lblMeaaseg = new Label();
lblMeaaseg.ID = "txtMessage";
lblMeaaseg.Text = "Hello Shree";
this.form1.Controls.Add(lblMeaaseg);
}
You create the dynamic button in the click event handler of btnMain during the postback caused by btnMain click. After that you see the new button in the browser page, click it and expect its click event handler (btnNew_Click) to fire. Pressing the new dynamic button causes a new postback that is processed by a new instance of the page created on the server by ASP.NET. This new page does not have the dynamic button - there is nothing there connected to btnNew_Click. You have to write code that persists the fact that the dynamic button has been created and recreates this button every time the page is instantiated. So that this button has a chance to feel and respond to its client-side click.
Basically, I have an update panel in which i have a link button, when user clicks on the link button all the contents are cleared and textbox shows up in which user enters something and when user hit enter key, the update panel should be refreshed or gets updated or repopulated with all the contents .
How can I do it ???
The way I am trying to do this is that when event handler of link button is fired, I created a hidden button dynamically and assign it a new event handler which will get fired when user hits enter key.This new dynamic button is created inside link button event handler. In this new button event handler I will repopulate the contents back.
The problem with my way is the event handler of dynamically created button is not fired.
Why ???
Please try to answer in c#.
Thanks in advance.
Regards,
My code #
protected void Submit_Click1(object sender, EventArgs e)
{
Label1.Text = TextBox1.Text + TextBox2.Text + " are sucessfully registered";
Button mento = new Button();
mento.cssclass = "invisible";
mento.Click += new EventHandler(mento_click);
// here this new mento button is attached to update panel
updatepanel1.ContentTemplateContainer.Controls.add(mento);
}
Now the problem is mento_click event handler does not get fired ???
You can catch the enter key, in the textbox?
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
//add event keydown
textBox1.KeyDown += new KeyEventHandler(textBox1_KeyDown);
}
void textBox1_KeyDown(object sender, KeyEventArgs e)
{
switch (e.KeyCode )
{
case Keys.Enter:
//YOur updatecode here:
MessageBox.Show("You press enter");
break;
default:
break;
}
}
}
You have to attach the event on page_init or page_load every time theres a request, or the event wont get hooked up to the control.
you can check out this link to understand why:
http://msdn.microsoft.com/en-us/library/ms178472.aspx
Example
if you want to hook it up on the submit you should do something like:
page_init(object sender, EventArgs e)
{
CreateControls();
}
private void CreateControls()
{
//Create button with event and add to the panel
}
clickEvent(object sender, EventArgs e)
{
updatePanel.Update();
}
That should fire correctly the event. Im sorry i just wrote this on the fly and didnt test it, but i hope it gives you de general idea.
Cheers.
To all of you strugling with postback from buttons in asp.net, I would like to mention an alternative and ancient method of dealing with button-click events.
1) name your dynamically created buttons using a Prefix (like for instance this one: btn_). That way, every button you create will have a name starting with this prefix. For example the first button you create will have the name btn_0. You can achieve this by a routine like this one:
For _counter As Integer = 0 To 3
Dim butt As New Button
' the next 1 line is convenient when programming for the .net 4.0 framework:
butt.ClientIDMode = UI.ClientIDMode.Static
butt.butt.ID = "btn_" & _counter
butt.Text = "someting"
page.controls.add(butt)
next
2) ... and then, to handle it all, you can do it like this in the on_load event of your asp.net page:
If IsPostBack Then
For Each key As String In Request.Form
If InStr(Trim(key), "btn_") > 0 Then
Response.Write(Request.Form(key))
End If
Next
End If
Good morning everybody.
I have a question connected with controls and event handling. Lets say I want to create a LinkButton.
protected void loadLinkButton()
{
ContentPlaceHolder content = (ContentPlaceHolder)this.Master.FindControl("MainContent");
LinkButton lnk = new LinkButton();
lnk.ID = "lnikBtn";
lnk.Text = "LinkButton";
lnk.Click += new System.EventHandler(lnk_Click);
content.Controls.Add(lnk);
}
Here is the event handler:
protected void lnk_Click(object sender, EventArgs e)
{
Label1.Text = "ok!";
}
If I run the loadLinkButton function inside Page_Load everything is ok. But when I try to run the loadLinkButton by clicking simple button, link button is created but event is not handled.
protected void Button1_Click(object sender, EventArgs e)
{
loadLinkButton();
}
I there any way to solve it? Or loadLinkButton must always regenerated on Page_Load, Page_init etc.
When working with dynamic controls, I always add the control in Page_Init, because viewstate loading will happen right after Init. If you add it to Page_Load, there is a chance that you will lose viewstate. Just make sure you provide a unique control ID.
It is important to know how ASP.Net determines which events to invoke. The source of each event is passed using a hidden field:
<input type="hidden" name="__EVENTTARGET" value="" />
Whenever the page loads, it pulls in the source of the event from that field and then determines which event to invoke. Now this all works great for controls added through markup because the entire control tree is regenerated on every request.
However, your control was only added once. When a Postback occurs, your control no longer exists as a Server control in the tree, and therefore the event never fires.
The simply way to avoid this is to make sure your Dynamic Controls are added every time the page loads, either through the Page_Init event, or the Page_Load event.
You are right. This is the expected behavior. Page_Load and Page_Init would be the events where you should be adding it.
That would be because when you click your dynamically generated linkbutton, you do a postback to the server. There you do an entirely new pageload, but your original buttonclick (that generates the link) never happened now, so the linkbutton is never made, and the event can not be thrown.
An alternative is to add the linkbutton you add dynamically, to your page statically, with Visible = false. And when you click the other button, make it visible.
I am not exactly sure what problem you are facing but you should put the dynamic controls code in Page_Init as suggested by #johnofcross:
public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Page_Init(object sender, EventArgs e)
{
CreateControls();
}
private void CreateControls()
{
var lb = new LinkButton();
lb.Text = "Click Me";
lb.Click += lb_Click;
ph.Controls.Add(lb);
ph.DataBind();
}
void lb_Click(object sender, EventArgs e)
{
lblMessage.Text = "Button is clicked!";
}
}