public bool VerificaLogin()
    {
        bool result = false;
        string StringDeConexao = "SERVER = localhost; DATABASE = global; UID = root; PASSWORD=";

            using (MySqlConnection cn = new MySqlConnection())
            {
                cn.ConnectionString = StringDeConexao;

                try
                {
                        MySqlCommand cmd = new MySqlCommand("SELECT * FROM usuarios WHERE login = '" + txtlogin.Text + "'AND senha = '" + GerarHashMd5(txtsenha.Text) +  "';", cn);
                        cn.Open();
                        MySqlDataReader dados = cmd.ExecuteReader();

                        result = dados.HasRows;
                }
                catch (MySqlException e)
                {
                    MetroFramework.MetroMessageBox.Show(this, "" + e.Message, "Erro", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                }
                finally
                {
                    cn.Close();
                }
            }
            return result;
    }

    public bool Logado = false;

private void btnentrar_Click(object sender, EventArgs e)
        {
           bool result = VerificaLogin();

           Logado = result;

           if (result)
           {
               MetroFramework.MetroMessageBox.Show(this, "Seja Bem-vindo", "Sucesso", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
               this.Close();
           }
           else
           {
               MetroFramework.MetroMessageBox.Show(this, "Usuário e/ou senha incorretos", "Erro", MessageBoxButtons.OK, MessageBoxIcon.Warning);
           }
       }