Question

I’ve read a few articles on here and the web that have informed me that I cannot simply add a new control dynamically to the page, wire it to a handler, and expect it to work.

The solution given each time is that the dynamic controls need to be added to the page on Init each time.

My problem is, my controls are NOT added to the page on init, they are added after ANOTHER postback.

the workflow is this:

1. Page Loads
2. User fills in a textbox, clicks a button
3. Page Posts back, creating dynamic link controls in the button_click event based on the input
4. User clicks one of those link controls to proceed to the next step.

so if this is the behavior I need to support, is there any way to do this? It has to happen in the button_click of step 2, because the dynamic controls are based on the input the user puts in step 2.

have I painted myself into a corner here? how else could I handle such a workflow?

Answer 1

After you dynamically create a link button, set a flag in your page’s view state. On postback, re-create the link button if the flag is set in view state. Here’s a demo:

Markup:

<asp:Button runat="server" ID="button1" OnClick="button_Click" Text="Create button A" CommandArgument="A" />
<asp:Button runat="server" ID="button2" OnClick="button_Click" Text="Create button B" CommandArgument="B" />
<asp:PlaceHolder runat="server" ID="placeHolder"></asp:PlaceHolder>

Code-behind:

public partial class Default : System.Web.UI.Page
{
    private bool LinkButtonCreated
    {
        get { return ((bool?)this.ViewState["LinkButtonCreated"]).GetValueOrDefault(); }
        set { this.ViewState["LinkButtonCreated"] = value; }
    }

    private string LinkButtonCommandArgument
    {
        get { return (string)this.ViewState["LinkButtonCommandArgument"]; }
        set { this.ViewState["LinkButtonCommandArgument"] = value; }
    }

    protected override void LoadViewState(object savedState)
    {
        base.LoadViewState(savedState);
        if (this.LinkButtonCreated)
            this.CreateLinkButton(this.LinkButtonCommandArgument);
    }

    protected void button_Click(object sender, EventArgs e)
    {
        if (!this.LinkButtonCreated)
        {
            string commandArgument = ((Button)sender).CommandArgument;
            this.LinkButtonCreated = true;
            this.LinkButtonCommandArgument = commandArgument;
            this.CreateLinkButton(commandArgument);
        }
    }

    private void CreateLinkButton(string commandArgument)
    {
        LinkButton linkButton =
            new LinkButton
            {
                ID = "linkButton",
                Text = "Click me",
                CommandArgument = commandArgument,
            };
        linkButton.Click += this.linkButton_Click;
        this.placeHolder.Controls.Add(linkButton);
    }

    private void linkButton_Click(object sender, EventArgs e)
    {
        LinkButton linkButton = (LinkButton)sender;
        linkButton.Text = "I was clicked! Argument: " + linkButton.CommandArgument;
    }
}