Why the number in ddl is not properly passed to the controller - asp.net-mvc

Question

In view, I have a dropdownlist control that I fill out by calling a function through a jQuery and DDL is filled correctly and there are no problems so far.
But when I pass the DDL value to the controller, if the value is alphabetical and a number, then the numeric value is not passed.
View:
<div class="form-group col-md-6">
<div class="col-md-10">
<select id="DDLMachintypeID" name="DDLMachintypeID" class="form-control"></select>
</div>
</div>
#section MyScripts
<script type="text/javascript">
$(function () {
$('#MachineID').change(function () {
var machineid = $(this).val();
$.ajax({
type: "post",
dataType: "json",
contentType: "application/json; charset=utf-8",
url: "FillTypes",
data: "{MachinKindId:'" + machineid + "'}",
success: function (data) {
$('#DDLMachintypeID').empty();
$.each(data, function (i, d) {
$('#DDLMachintypeID').append('<option selected="selected" value=' + d + '>' + d + '</option>');
});
},
failure: function (data) {
alert('error occured');
}
});
});
});
</script>
End Section
and in controller:
Dim strDDL = Request.Form("DDLMachintypeID")
For example if my dropdown's selected value is A3, in controller I get A!
Only an alphanumeric string is passed to the controller. The strDDL that I read is only A while it should be A3. Why ?!

Answer 1

problem solved
This section edited the jquery code in the following format:
$.each(data, function (i, d ) {
$('#DDLMachintypeID').append('<option selected="selected" value="' + d + '">' + d + '</option>');
});