Question

public partial class Default2 : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {
        GenerateButtons generate = new GenerateButtons();
        generate.Generate5Controls(PlaceHolder1);

    }


}


class GenerateButtons
{
    PlaceHolder placeHolder;
   public  void Generate5Controls(PlaceHolder placeH)
    {
        placeHolder = placeH;
        for (int i = 0; i < 5; i++)
        {
            Button newBtn = new Button();
            newBtn.Click += btn_Click;
            newBtn.Text = "PageLoadButton Created. Number: "+i;
            placeHolder.Controls.Add(newBtn);
        }
    }
    public void btn_Click(object sender, EventArgs e)
    {
        Button newBTN = new Button();
        newBTN.Text = "A New Button was added by the button event btn_click";
        newBTN.Click += btn2_Click;
        placeHolder.Controls.Add(newBTN);

    }
    public void btn2_Click(object sender, EventArgs e)
    {
        Button newBTN = new Button();
        newBTN.Text = "A New Button was added by the button event btn2_click";
        placeHolder.Controls.Add(newBTN);
    }
}

I want the events btn_click & btn2_click to fire every post back.. When i click the button that was programmatically created it disappears after each postback and its event doesnt fire (btn2_click). I know i could generate the button at the postback.. But I dont want to do that!! I want to know how I could update the state of the placeholder… so that the only button will appear and the 5 buttons generated in Generate5Controls(PlaceHolder placeH) to disappear.

I could use a bool Viewstate to prevent this generate.Generate5Controls(PlaceHolder1); from being execute..

But the question is how do I make the programmatically generated button to appear!?

Answer 1

You should generate controls on every PostBack or you can generate controls once, save in session and add generated controls from session on page_load event.

protected void Page_Load(object sender, EventArgs e)
    {
       if(Session["GeneratedButtons"] == null)
       {
          GenerateButtons generate = new GenerateButtons();
          generate.Generate5Controls(PlaceHolder1);
       }
       else
       {
           List<Control> generatedControls = Session["GeneratedButtons"] as List<Control>;
           foreach(Control oneControl in generatedControls)
           {
               PlaceHolder1.Controls.Add(oneControl);
           }
       }
    }

class GenerateButtons
{
    PlaceHolder placeHolder;
   public  void Generate5Controls(PlaceHolder placeH)
    {
        placeHolder = placeH;
        List<Control> generatedControls = new List<Control>();
        for (int i = 0; i < 5; i++)
        {
            Button newBtn = new Button();
            newBtn.Click += btn_Click;
            newBtn.Text = "PageLoadButton Created. Number: "+i;
            placeHolder.Controls.Add(newBtn);
            AddControlToSession(newBtn);
        }
    }
    public void btn_Click(object sender, EventArgs e)
    {
        Button newBTN = new Button();
        newBTN.Text = "A New Button was added by the button event btn_click";
        newBTN.Click += btn2_Click;
        placeHolder.Controls.Add(newBTN);
        AddControlToSession(newBtn);
    }

    public void btn2_Click(object sender, EventArgs e)
    {
        Button newBTN = new Button();
        newBTN.Text = "A New Button was added by the button event btn2_click";
        placeHolder.Controls.Add(newBTN);
        AddControlToSession(newBtn);
    }

    private void AddControlToSession(Control ctrl)
    {
        List<Control> generatedControls = Session["GeneratedButtons"] as List<Control>;
        if(generatedControls == null)
        {
            generatedControls = new List<Control>();
        }
        generatedControls.Add(ctrl);
        Session["GeneratedButtons"] = generatedControls;
    }
}