this way
DataSet ds = new DataSet();
OracleDataAdapter ndadptr = new OracleDataAdapter("SELECT * FROM "+ listBox1.SelectedItem.ToString(), OrConn.conn);
ndadptr.Fill(ds);
dataGridView1.DataSource = ds.Tables[0];
dataGridView1.DataMember = ds.Tables[0].Name;
then you will able to retrieve datamember
Happy Coding!
:)