error incorrect syntax near & c#

cmd.CommandText = "select username , password from passwords where username='"
                    + textBox1.Text + "' && password='" + textBox2.Text + "'";
                object obj = cmd.ExecuteScalar();

                if (obj == null) // No such username or password exist
                    label5.Text = "NotValid";
                else
                {
                    label5.Text = "Valid";
                }