ASP.NET

public static void SetFocus(Control control)<br />
{<br />
    StringBuilder sb = new StringBuilder();<br />
 <br />
    sb.Append("\r\n<script language='JavaScript'>\r\n");<br />
    sb.Append("<!--\r\n"); <br />
    sb.Append("function SetFocus()\r\n"); <br />
    sb.Append("{\r\n"); <br />
    sb.Append("\tdocument.");<br />
 <br />
    Control p = control.Parent;<br />
    while (!(p is System.Web.UI.HtmlControls.HtmlForm)) p = p.Parent; <br />
 <br />
    sb.Append(p.ClientID);<br />
    sb.Append("['"); <br />
    sb.Append(control.UniqueID); <br />
    sb.Append("'].focus();\r\n"); <br />
    sb.Append("}\r\n"); <br />
    sb.Append("window.onload = SetFocus;\r\n"); <br />
    sb.Append("// -->\r\n"); <br />
    sb.Append("</script>");<br />
 <br />
    control.Page.RegisterClientScriptBlock("SetFocus", sb.ToString());<br />
}

<script language='JavaScript'><br />
<!--<br />
function SetFocus()<br />
{<br />
    document.Form1['TextBox1'].focus();<br />
}<br />
window.onload = SetFocus;<br />
// --><br />
</script>

protected string MyMethod(string s)
{
    return Server.UrlEncode(s);
}