copy data from 1 datatable to another

There are multiple ways to copy data from 1 datatable to another.
a)dtnew=dtold.copy();
copies both structure and data
b)dtnew=dtold,clone()
copies only structure.
(we can use it instead of adding columns)

c)
to copies data of specific columns

    DataTable dtnew=new DataTable();

            dtnew.Columns.Add("sl_no");

            dtnew.Columns.Add("Tenant");

            foreach(DataRow dr in dt.Rows)

            {

                DataRow drNew = dtnew.NewRow();

                drNew["sl_no"]=dr["slno"];

                drNew["Tenant"] = dr["tenant_name"];

                dtnew.Rows.Add(drNew);

            }