When I run this code I get alert saying Error.

My Code:

<script type="text/javascript">
    debugger;
    $(document).ready(function () {
        SearchText();
    });
    function SearchText() {
        $(".auto").autocomplete({
            source: function (request, response) {
                $.ajax({
                    type: "POST",
                    contentType: "application/json; charset=utf-8",
                    url: "Default.aspx/GetAutoCompleteData",
                    data: "{'fname':'" + document.getElementById('txtCategory').value + "'}",
                    dataType: "json",
                    success: function (data) {
                        response(data.d);
                    },
                    error: function (result) {
                        alert("Error");
                    }
                });
            }
        });
    }
</script>

 [WebMethod]
 public static List<string> GetAutoCompleteData(string CategoryName)
    {
        List<string> result = new List<string>();
        using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["DbConnection"].ConnectionString))
        {
            using (SqlCommand cmd = new SqlCommand("select fname from tblreg where fname LIKE '%'+@CategoryText+'%'", con))
            {
                con.Open();
                cmd.Parameters.AddWithValue("@CategoryText", CategoryName);
                SqlDataReader dr = cmd.ExecuteReader();
                while (dr.Read())
                {
                    result.Add(dr["fname"].ToString());
                }
                return result;
            }
        }
    }

I want to debug my function GetAutoCompleteData but breakpoint is not fired at all. What's wrong in this code? Please guide. I have attached screen shot above.