Login Form with Permissions for users

SqlConnection con;
        SqlCommand com;
        SqlDataAdapter da;

        public DataAccess()
        {
            con = new SqlConnection();
            com = new SqlCommand();
            da = new SqlDataAdapter();
            com.Connection = con;
            da.SelectCommand = com;
        }

        public void Connect()
        {
            con.ConnectionString = @"Data Source=.;Initial Catalog=Test;Integrated Security=True";
            con.Open();
        }

        public void Disconnect()
        {
            con.Close();
        }

        public void Execute(string SQL)
        {
            com.CommandText = SQL;
            com.ExecuteNonQuery();
        }

        public DataTable SELECT(string SQL)
        {
            DataTable dt = new DataTable();
            com.CommandText = SQL;
            da.Fill(dt);
            return dt;
        }

DataAccess DA = new DataAccess();

        public static bool M = false;
        public static bool S = false;
        public static bool B1 = false;
        public static bool B2 = false;

        public int ID;
        public string Nam;
        public string Pas;
        public bool Mnu;
        public bool Str;
        public bool Btn1;
        public bool Btn2;

        public void Sath(string name)
        {
            DA.Connect();
            string sql = "Select * From User Where Nam = '{0}' ";
            sql = string.Format(sql, name);
            DataTable dt = DA.SELECT(sql);
            DA.Disconnect();

            M = Convert.ToBoolean(dt.Rows[0]["Mnu"].ToString());
            S = Convert.ToBoolean(dt.Rows[0]["Str"].ToString());
            B1 = Convert.ToBoolean(dt.Rows[0]["Btn1"].ToString());
            B2 = Convert.ToBoolean(dt.Rows[0]["Btn2"].ToString());
        }

        public bool Login(string Name, string Pass)
        {
            DA.Connect();
            string sql = "Select Count(*) From User Where Nam = '{0}' And Pas = '{1}'";
            sql = string.Format(sql,Name,Pass);
            DataTable dt = new DataTable();
            dt = DA.SELECT(sql);
            DA.Disconnect();

            bool Enter = false;
            if (dt.Rows[0][0].ToString() == "1")
            {
                Enter = true;
            }
            return Enter;
        }

        public void ADD()
        {
            DA.Connect();
            string sql = "Insert Into User (ID,Nam,Pas,Mnu,Str,Btn1,Btn2)";
            sql += "Values ({0},'{1}','{2}','{3}','{4}','{5}','{6}')";
            sql = string.Format(sql, this.ID, this.Nam, this.Pas, this.Mnu, this.Str, this.Btn1, this.Btn2);
            DA.Execute(sql);
            DA.Disconnect();
        }

        public DataTable ShowData()
        {
            DA.Connect();
            DataTable dt = DA.SELECT("Select * From User");
            DA.Disconnect();
            return dt;
        }

Users us = new Users();
            if (us.Login(textBox2.Text, textBox1.Text) == true)
            {
                us.Sath(textBox2.Text);

                this.Hide();
                Form2 f2 = new Form2();
                f2.Show();
            }
            else
                MessageBox.Show("unvalid pass");