focus on control after page load

You try any of the ways as below

1. Set directly form tag of your page. Or

2. Or in PageLoad event try InputControlId.Focus();

if you want to set through clientside you try as Rockstar's solution.

Hope this helps...

one more way

Declare JavaScript block in your content page like below

<%@ Page Language="C#" MasterPageFile="~/Site1.Master" AutoEventWireup="true" CodeBehind="WebForm2.aspx.cs" Inherits="WebApplication4.WebForm2" Title="Untitled Page" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
    <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
    <asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>
    <script>
    var controlId_focus= '<%=controlIdForFocus%>';
    function CallSetFocus(){
      if(controlId_focus !="" && document.getElementById(controlId_focus)!=null)    {
        document.getElementById(controlId_focus).focus();
      }
    }
     setTimeout('CallSetFocus()',200);
    </script>
</asp:Content>

Now in your code behind file declare protected string "controlIdForFocus" and assign ClientID of a control where you want focus like below code snippet

public partial class WebForm2 : System.Web.UI.Page
   {
       protected string controlIdForFocus = "";
       protected void Page_Load(object sender, EventArgs e)
       {
           controlIdForFocus = TextBox3.ClientID;
       }
   }