To generate 1+ value in combobox from a integer column of sql server

Dear Friends I have to generate 1+ value from maximum available in column of table for that I have one stored procedure As shown below

ALTER procedure generateid
as
begin
select max("pid")+1 from pinfo
end


And in datalayer i have called it in this way

public DataSet generateid()
        {
           
           
                con = new SqlConnection("integrated security=true;database=hm");
            cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandType = CommandType.StoredProcedure;
                cmd.CommandText = "generateid";
              
                da = new SqlDataAdapter(cmd);
                DataSet ds = new DataSet();
                da.Fill(ds, "pinfo");
                return ds;

            }

and from front end I have tried to get value in following way

              DL gi = new DL();
            DataSet ds = gi.generateid ();
            comboBox1 .DataSource = ds.Tables["pinfo"] ;
            comboBox1 .DisplayMember = "pid";


but it is coming as  System.Data.DataRowView
please suggest me solution