Run time the user control content not displaying to the page
<p>I have a  few user  controls, and on ASPX page on some drop down selection change i am adding user control this way, the user contorl not being displayed what i am unable to fix on it, please let me know where i am going wrong.</p>

<p>partial code</p>

<pre><code>  switch (ContentTypeID)
        {
            case 1:
                UserControl uc = new UserControl();

            //string ID = "1";
                //string userControl ="UC" + ID + ".ascx";
                //uc = LoadControl(userControl) as UserControl;
                //PlaceHolder1.Controls.Add(uc);
                uc.LoadControl("~/Controls/DocumentSpreadSheet.ascx");
                //Control myUserControl = (Control)Page.LoadControl("~/Controls/DocumentSpreadSheet.ascx");
                pnlDetails.Controls.Add(uc);
                break;
            case 2:
                break;
            case 3:
</code></pre>
