Try this solution..
In View ..
<html.textboxfor(model> model.Mobile, new { maxlength = 10, style = "width:145px", @onblur = "return Validate Phone()" })/>
.
.
<input type="submit" id="save" value="save" />
In Script...
<script type="text/javascript">
function ValidatePhone() {
debugger;
var phoneVal = $("#Mobile").val();
var number = phoneVal.length;
if (10 <= number) {
alert("SUCCESS");
$("#save").attr('disabled', false);
}
else {
alert("check number");
$("#save").attr('disabled', true);
}
}
</script>