private void buttonback_Click(object sender, EventArgs e)
        {
            welcome_manager f = new welcome_manager();

            f.Show();
            this.Hide();
        }
        private void buttonlogin_Click(object sender, EventArgs e)
        {
            if (textBoxname.Text != "" && textBoxid.Text != "")
            {
                Class_DB db = new Class_DB();
                db.ConnectDB();
                DataSet ds = new DataSet();
                ds = db.selectdb("Select * from [user] where user_name='" + textBoxname.Text + "' and password='******'", "User");

                if (ds.Tables["User"].Rows.Count >= 1)
                {
                    welcome_manager f = new welcome_manager();
                    f.Show();
                    this.Hide();
                }
                else
                {
                    label4.Text = "your Name or your Password not Vaild";
                }
            }
            else
            {
                label4.Text = "your must Enter your Name and your Password";
            }
        }