Setting focus on TextBox within asp:panel and contentplaceholder

Ok
I have a project with several pages all using 1 master page.
I need to set focus onto a textbox either on page load or on a button click.


The textbox is in a panel on one of the child pages of the master page like this:
<asp:contentplaceholder ID="content1">
     <asp:panel ID="Panel1">
          <asp:TextBox ID="TextBox1">

     </asp:panel>
</asp:contentplaceholder>


I have tried all kinds like:
page_load()
{
   //    Page.SetFocus(TextBox1.ClientID);
   //    Page.SetFocus(TextBox1);
   //    TextBox1.Focus();


  //     TextBox Test = (TextBox)Panel1.FindControl("TextBox1");
       ...