Hi,

write your method as follows if you have no rows in your database it will automatically returns all columns with zero rows

SqlConnection cn = new SqlConnection("Data Source=.;database=NorthWind;user id=sa;password=sa@123");
        [OperationContract]
        public DataSet GetData()
        {
            DataSet ds = new DataSet();
            SqlDataAdapter da = new SqlDataAdapter("select * from Emp", cn);
            da.Fill(ds, "Emp");
            return ds;
        }

and calling from client as follows

  ServiceRef.Service1Client cleint = new ServiceRef.Service1Client();
            DataSet ds = cleint.GetData();

Hope it will solve your problem.

Please mark as answer if post is solved your problem

Thanks