Give it a shot:
Using Jquery:
$(document).ready(function() {
$("#dropdounid").prop("disabled", true);
});
OR
$(document).ready(function() {
$("#dropdounid").attr("disabled", true);
});
Or, with Javascript:
To disable an Asp.net DropDownList
using JavaScript on the client side, you can use the following code.
document.getElementById('<%=txtActualWindSpeed.ClientID%>').disabled = true;
Edit:
To implement this code, place it within either the head tag or body tag
.
<head>
<script>
document.getElementById('<%=txtActualWindSpeed.ClientID%>').disabled = true;
</script>
</head>
I trust that this will be of assistance to you.
Check out the jsfiddle Demo