这是我设置登录的，为什么if里面的语句没有执行，显示的就是”输入有误“ 我是2010版C#

 private void button1_Click(object sender, EventArgs e)
        {
            string txt1 = "Data Source=pc2011091520fha;DataBase=学生;Integrated Security=SSPI;User Instance=False";
            SqlConnection conn = new SqlConnection(txt1);
            string sql = "select * from [zhuce]";
            SqlCommand cmd = new SqlCommand(sql, conn);
            conn.Open();
            SqlDataReader reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                bool s=reader["Z_no"].ToString () == textBox1.Text.Trim() && (reader["passw"].ToString () == textBox2.Text.Trim());
                if (s ==true)
                {
                    MessageBox.Show("登录成功！");
                    
                    conn.Close();
                    reader.Close();
                    frmain fmain = new frmain();
                    fmain.Show();
                    
                    textBox1.Text = "";
                    textBox2.Text = "";
                    
                }
                else
                {
                    MessageBox.Show("输入有误!"); break;
                  
                          

                }  
            }                    

        }

其中语法没有错误了