Dynamically assign button events in c# asp.net

Question

Can you please tell me what's wrong with the following code?

        Panel div = new Panel();
        Button btn1 = new Button { Text = "Delete", CommandArgument = "argument", ID = "remove" };
        Button btn2 = new Button { Text = "Insert", CommandArgument = "argument2", ID = "insert" };

        btn1.Click += new EventHandler(btn_click);
        btn2.Click += new EventHandler(btn_click);

        div.Controls.Add(btn1);
        div.Controls.Add(btn2);

        ph_plan.Controls.Add(div); // where ph_plan is a placeholder in the user control

protected void btn_click(object sender, EventArgs e)
{
    Button btn = (Button)sender;
    if(btn.ID == "remove")
        // do this
    else 
        // do that
}

The code above occurs right after a click on a button in the user form. It is supposed to create 2 new buttons with events assigned. Indeed, it creates the buttons but when I click them nothing happens. I guess the events cannot be registered. What am I doing wrong here?

done, but please bear in mind that the problem is that the event is not fired. — Shaokan
– Shaokan, Commented May 9, 2011 at 15:58

keyboardP · Accepted Answer · 2011-05-09 15:56:05Z

6

The reason this is happening is because Page is a stateless class and once it renders everything, it is destroyed. Therefore, once you have a postback, this information is lost and your Page class has no knowledge of the button's events since the dynamic buttons were not part of the aspx file.

You need to maintain a collection of the dynamic controls that you've created, possibly in a session, so that they can be recreated after a postback. There's an example of it here.

answered May 9, 2011 at 15:56

keyboardP

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3 Comments

Josh M. Over a year ago

E.g. the buttons need to be recreated on post-back otherwise they don't exists and hence, neither does the event wiring.

keyboardP Over a year ago

Exactly. Although ASP.NET development is similar to WinForms in terms of creating and manipulating objects, the thought process is very different and it's easy to forget the stateless nature of the web.

Shaokan Over a year ago

ok, thanks done :) I've created a cache after the buttons are created and in the page_init event if the cache in question is found it re-creates the buttons. Now, it's working! Thanks again!

Drew Noakes · Accepted Answer · 2012-12-30 18:27:52Z

0

How to create multiple control in asp.net with event:

string[] arg = new string[10];

protected void Page_Load(object sender, EventArgs e)
{

    for (int i = 0; i < 10; i++)
    {
        LinkButton bb = new LinkButton();
        arg[i]= bb.ID = "bb" + i.ToString();
        bb.Text = "like"+"<br/>";
        Panel1.Controls.Add(bb);
        bb.Click += new EventHandler(bb_Click);
    }
}

void bb_Click(object sender, EventArgs e)
{
    LinkButton btn = (LinkButton)sender;
    for (int j = 0; j < 10; j++)
    {
        if (btn.ID == arg[j])
        {
            btn.Text = "";
            btn.Text = "unlike";
            Response.Write(arg[j]);
        }
    }
}

This code will print every button id that have been created at runtime in page load event.

edited Dec 30, 2012 at 18:27

Drew Noakes

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answered Dec 30, 2012 at 18:09

shailesh kumar

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