Question

I am making a C# Web Application in .Net

I have overridden the Panel control to make a div clickable. It looks like this:

public class ProjectPanel : System.Web.UI.WebControls.Panel, System.Web.UI.IPostBackEventHandler
{
    public ProjectPanel() 
    {
        CssClass = "project";
        this.Click += new EventHandler(ProjectPanel_Click);
    }

    public event EventHandler Click;

    protected virtual void OnClick(EventArgs e)
    {
        if (Click != null)
        {
            Click(this, e);
        }
    }

    public void RaisePostBackEvent(string eventArgument)
    {
        OnClick(new EventArgs());
    }

    protected override void Render(System.Web.UI.HtmlTextWriter writer)
    {
        this.Attributes.Add("onclick", "__doPostBack('" + this.ClientID + "', '');");
        base.Render(writer);
    }
    public void ProjectPanel_Click(object sender, EventArgs e)
    {
        Label l = new Label();
        l.Text = " HIYA";
        this.Controls.Add(l);
    }
}

Now, this works fine inside a Page. However, I also have a Web User Control which looks like:

<div class="team">

<asp:Panel runat="server" ID="TheCanvas" CssClass="projects" />

</div>

Now when I add the overriden Panel to the TheCanvas panel, the click event isnt registered anymore. The postback happens, but the ProjectPanel_Click doesnt fire. Any ideas? I’m adding the panel through code.

Answer 1

Instead of ClientID you should use UniqueID because when in another control client ID is prefixed with parend client ID, replace onclick attribute setting with this :

this.Attributes.Add("onclick", "__doPostBack('" + this.UniqueID + "', '');");

btw. you should be aware that if you don’t have on page another control that implements IPostBackDataHandler, __doPostback javascript would not be present and you will get javascript error:

__doPostBack is not defined

You should implement IPostBackDataHandler and call Page.RegisterRequiresPostBack(this) inside your panel control, see details on this links:

http://aspalliance.com/1071_Smart_ListControl_in_ASPNET_1x20.4

http://www.timvasil.com/blog14/post/2007/10/30/Implementing-IPostBackDataHandler-once-and-for-all.aspx