enable second textbox when text enters in first textbox

try this hope it will help you

if(TxtCountry.Text=="")
{
    txtcity.enable=false;
}
else
{
    txtcity.enable=True;
}

Hi,
you can do it by enabling keyup event of Txtcountry.

$("#<%= TxtCountry %>").keyup(function (event) {
      if($("#<%= TxtCountry %>").val() == '')
      {
          $("#<%= TxtCity %>").attr("disabled", "disabled"); 
      }
      else
      {
          $("#<%= TxtCity %>").removeAttr("disabled");
      }
   });

Hope it helps.

I have a Solution...
Add two text box like this..

<asp:textbox id="TxtCountry" onkeypress="change()" runat="server"></asp:textbox>
       <br />
<asp:textbox id="Txtcity" runat="server" enabled="False"></asp:textbox>

Then set enabled=false property of TxtCountry.
After that just write the javascript to that page like below..

<pre lang="Javascript"><script type="text/javascript">
        function change() {
            document.getElementById("Txtcity").disabled = false;
        }
    </script>

Don't forget to add script manager to the page...
I hope you satisfied with this solution...
Have a good day..