Creating a Service in C#

Goto to add new Item from your Project
Add WebService.asmx
one file is added under App_Code folder WebService.cs
Goto That file
Here you have to write which method you want to create..Here i am giving you an example:

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService]
[WebMethod]//added these else code doesn't work
public List<City> GetNews()
{
    List<City> list = new List<City>();
    string constr = "Data Source=localhost;Initial Catalog=DBname;User Id=sa;Password=lock";
    string query = "SELECT top 20 news_id,news_title FROM news order by news_id DESC";
    SqlDataAdapter da = new SqlDataAdapter(query, con);
    DataSet ds = new DataSet();
    da.Fill(ds);
    list = ds.Tables[0].AsEnumerable().Select(data => new City() { Id = (int)data["news_id"], title = (string)data["news_title"] }).ToList();
    return list;
}
public class City
{
    public int Id { get; set; }
    public string title { get; set; }
}

Now i have called these web service from another page like this way

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script type="text/javascript">
    $(document).ready(function () {
        $.ajax({
            type: "POST",
            url: "WebService.asmx/GetNews",
            data: "{}",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (response) {
                var cars = response.d;
                $('#output4').empty();
                $.each(cars, function (index, car) {
                    var url = "Mobile.aspx?id=" + car.Id;
                    $('#output4').append('<li><a href="' + url + '">' + car.title + '</a></li>');
                });
                $('#output4').append('<li style="color:Red; font-size:small; text-align:right"><a href="AllMobiles.aspx">view more</a></li>');
            },
            failure: function (msg) {
                $('#output4').text(msg);
            }
        });
    });
</script>

If you still having problem feel free to ask...always here to support...