private void VisualizzaDatiInGridView(string tableName)
{
    using (SqlConnection conn = new SqlConnection(stringa_di_connessione))
    {

        using (SqlCommand comm = new SqlCommand(string.Format ("SELECT * FROM {0}",tableName ), conn))
        {

            conn.Open();

            SqlDataReader reader = comm.ExecuteReader(System.Data.CommandBehavior.CloseConnection);

            if (reader.HasRows)
            {
                GridView1.AutoGenerateColumns = true;
                GridView1.DataSource = reader;
                GridView1.DataBind();
            }
        }
    }
}