private void Add_User_button_Click(object sender, EventArgs e)
 {
     try
     {
         Oracle.CreateUser(MainForm.Login_Form.conn, UserName_textBox.Text, Password_textBox.Text);
         MessageBox.Show("ĐA TAO USER " + UserName_textBox.Text + " THANH CONG!!", "Succeed", MessageBoxButtons.OK, MessageBoxIcon.Information);
         MainForm.GetUsers();
         this.Close();
     }
     catch (Exception ex)
     {
         MessageBox.Show("ERROR:" + ex.Message, "Fail", MessageBoxButtons.OK, MessageBoxIcon.Error);
     }
 }