web user control click event fires only from second click

See more:

C#

ASP.NET

WebForms

user-controls

A user control I add dynamically has an image with onClick event.
When the user control is added up the onClick event occours only from the second click and on.
Here is the .cs file of the webform:

Public partial class Site_DynamicPage : System.Web.UI.Page
{
    private static Control uc;
    private static string lastControl = null;

    private void loadDynamically()
    {
        if (lastControl != null)
        {
            PlaceHolder1.Controls.Clear();
            uc = Page.LoadControl("~/Site/Controls/" + lastControl + ".ascx");
            PlaceHolder1.Controls.Add(uc);     
        }
    }
    protected void Page_Load(object sender, EventArgs e)
    {
        loadDynamically();
    }
    protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        lastControl = ListBox1.SelectedValue;
        loadDynamically();
    }
}

Here a control is selected from the ListBox and appears on the PlaceHolder,
again the Click event of the user control doesn't fire on the first cilck.
Any solutions for this? Thax.