How to Convert Webservice Method to XmlDataDocument

using System.Xml;

[WebMethod(Description = "This is to Get Result", EnableSession = false)]
    public XmlDataDocument GetResults(string Value)
    {
        try
        {
            using (SqlConnection oCon = new SqlConnection(CONN_STRING_SQL))
            {
                DataSet odsWebService = new DataSet();
                SqlDataAdapter oAdap = new SqlDataAdapter("USP_WebService", oCon);               
                oAdap.SelectCommand.CommandType = CommandType.StoredProcedure;
                oAdap.SelectCommand.Parameters.AddWithValue("@iMode", 101);
                oAdap.SelectCommand.Parameters.AddWithValue("@Value", Value);               
                oCon.Open();
                oAdap.SelectCommand.ExecuteNonQuery();
                oAdap.Fill(odsWebService);
                oCon.Close();               
                result = new XmlDataDocument(odsWebService);
            }
        }
        catch (Exception ex)
        {
            DataSet ds = new DataSet();
            DataTable dt = new DataTable();
            dt.Columns.Add(new DataColumn("Message"));
            DataRow oDr = dt.NewRow();
            oDr["Message"] = "Please provide valid data, Thanks.";
            dt.Rows.Add(oDr);
            dt.AcceptChanges();
            ds.Tables.Add(dt);
            result = new XmlDataDocument(ds);
        }
        return result;
    }