c#连接access数据库问题

 private void button1_Click(object sender, EventArgs e)
        {
            string datacon = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=test.mdb";
            OleDbConnection conn = new OleDbConnection(datacon); //Jet OLEDB:Database PasswPersist Security Info=falseord=
            OleDbCommand cmd = conn.CreateCommand();

            cmd.CommandText = "select * from test";
            conn.Open();            
            OleDbDataReader dr = cmd.ExecuteReader();
            DataTable dt = new DataTable();
            if (dr.HasRows)
            {
                for (int i = 0; i < dr.FieldCount; i++)
                {
                    dt.Columns.Add(dr.GetName(i));
                }
                dt.Rows.Clear();
            }
            while (dr.Read())
            {
                DataRow row = dt.NewRow();
                for (int i = 0; i < dr.FieldCount; i++)
                {
                    row[i] = dr[i];
                }
                dt.Rows.Add(row);
            }
            cmd.Dispose();
            conn.Close();
            dataGridView1.DataSource = dt;
        

        }