about a web service retrieving data from MySQL database

I am trying to create a web service that can get data from MYSQL database but I have a problem

the web form code

namespace John
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!this.IsPostBack)
            {
                this.BindGrid();
            }
        }

        private void BindGrid()
        {
           localhost.Service1 service = new localhost.Service1();
            GridView1.DataSource = service.Get(); 
            GridView1.DataBind();
        }
    }
}

and the web service code

public DataTable Get()
        {
            string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand("SELECT * FROM nursery1"))
                {
                    using (SqlDataAdapter sda = new SqlDataAdapter())
                    {
                        cmd.Connection = con;
                        sda.SelectCommand = cmd;
                        using (DataTable dt = new DataTable())
                        {
                            dt.TableName = "nursery1";
                            sda.Fill(dt);
                            return dt;
                        }
                    }
                }
            }

I just follow the steps from this tutorial:

http://ift.tt/1kTz0RT

or if you have any useful reference about getting data from SQL database using web service in ASP.NET and C# please help me

thanks in advance