public partial class Form1 : Form
    {
        public string str = @"Data Source=DESKTOP-9I02IE1;Initial Catalog = trabalhoC#;Integrated Security=True;Pooling=False";
        public Form1()
        {
            InitializeComponent();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            MessageBox.Show("Adeus!");
            this.Close();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            SqlConnection sc = new SqlConnection(str);
            SqlDataAdapter sda = new SqlDataAdapter();
            DataSet ds = new DataSet();
            sda.SelectCommand = new SqlCommand("Select username,password from utilizadores where username = '"+textBox1.Text.ToString()+"' and password = '"+textBox2.Text.ToString() + "' ");
            sc.Open();
            sda.Fill(ds);
            if (ds.Tables[0].Rows.Count>0)
            {
                Form2 f = new Form2();
                f.Show();
            }
            else
            {
                MessageBox.Show("utilizador ou password incorrectas");
            }
            sc.Close();
        }