how to automatically change focus of text box when reach to max length

Hi,

Update your code as below.

private void txtcnic1_TextChanged(object sender, EventArgs e)
{
  if (txtcnic1.MaxLength == txtcnic1.Text.Length)
      txtcnic2.Focus();
}

And in your aspx page.

<asp:textbox id="txtcnic1" runat="server" ontextchanged="txtcnic1_TextChanged" AutoPostBack="true"></asp:textbox>

Please make sure you have set AutoPostBack property to true.

Hi
Try this

private void textBox1_TextChanged(object sender, EventArgs e)
     {
         if(textBox1.TextLength.Equals(textBox1.MaxLength))
             textBox2.Focus();
     }

Here is an approach using JavaScript

Here are the 2 text boxes. The Maxlength property of txtbox1 is set to 4. So after entering 4 characters in this text box the focus will be shifted to textbox txtbox2.

<asp:TextBox ID="txtbox1" runat="server" MaxLength="4"></asp:TextBox>
<asp:TextBox ID="txtbox2" runat="server"></asp:TextBox>

Here is the JavaScript that shifts the focus to textbox txtbox2.

<script type="text/javascript">
     
    function setFocus(MaxLength)
    {
        var txt1 =  document.getElementById('<%= txtbox1.ClientID%>');
        var txt2 =  document.getElementById('<%= txtbox2.ClientID%>');
        if(txt1.value.length == MaxLength)
        {
            txt2.focus();
        }
    }
    </script>

In your code behind file call the javascript function in page_Load.

txtbox1.Attributes.Add("onkeyup", "setFocus(" + txtbox1.MaxLength +")");