新手求助,关于修改密码页面,请大家帮忙,谢谢

Question

我初学c#，想做一个修改用户密码的窗体，连接的sql2000，我的思路是先连接数据库读取到该用户相应的密码，然后和textBoxOld对比，如果二者相等的话，继续验证新密码textBoxNew.Text和确认密码textBoxNewQueren.Text是否相等，若相等的话，就把新密码更新到原来的密码处。不知道这个思路怎么样，写了一部分，然后就不太会写了，请大家帮帮我，谢谢大家。
            if (textBoxNewQueren.Text == textBoxNew.Text)
            {
                
                SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=db_showHouse;Integrated Security=True");
                SqlCommand cmd = new SqlCommand("select (*) from tb_User", conn);//不知道这么写对不对....
                conn.Open();
                string aa = cmd.EndExecuteNonQuery();
                conn.Close();
                if (aa == textBoxOld.Text)
                { 
                    //更新数据库，不会写.......
                }
            }
            else
            {
                MessageBox.Show("您的密码输入有误，请重新输入！");
                textBoxNew.Text = "";
                textBoxNewQueren.Text = "";
            }

Answer 1

先找本书看吧，如Visual C# 2005 管理系统开发经典案例

Answer 2

  if (textBoxNewQueren.Text == textBoxNew.Text) 
            { 
                
                SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=db_showHouse;Integrated Security=True"); 
                SqlCommand cmd = new SqlCommand("select 密码 from tb_User where 用户名='"+用户名+"'", conn                conn.Open(); 
                string aa = （string）cmd.Excultscale(); 
                if (aa == textBoxOld.Text) 
                { 
                    cme.CommaneText ="Update tb_User  set 密码= '"+textBoxNew.Text+"' where 用户名='"+用户名+"'";
   cmd.ExcultNoQuery();
conn.Close();
                } 
else
{
MessageBox.Show("密码不匹配!");
}
            } 
            else 
            { 
                MessageBox.Show("新密码和确认密码不一致，请重新输入！"); 
                textBoxNew.Text = ""; 
                textBoxNewQueren.Text = ""; 
            }

Answer 3

        //记录用户登录次数
        private int MyTryCount = 0;
        private void 登录系统Button_Click(object sender, EventArgs e)
        {
                //从app.config文件中读取数据库连接字符串信息
                String MySQLConnectionString = global::MyHotel.Properties.Settings.Default.MyHotelConnectionString;
                string MySQL = "Select COUNT(*) From 操作用户 Where 用户名称=@用户名称 AND 用户密码=@用户密码";
                SqlConnection MyConnection = new SqlConnection(MySQLConnectionString);
                MyConnection.Open();
                SqlCommand MyCommand = new SqlCommand(MySQL, MyConnection);
                MyCommand.Parameters.Clear();
                SqlParameter MySqlNameParameter = new SqlParameter();
                MySqlNameParameter.ParameterName = "@用户名称";
                MySqlNameParameter.Value = this.用户名称TextBox.Text;
                MyCommand.Parameters.Add(MySqlNameParameter);
                SqlParameter MySqlPWParameter = new SqlParameter();
                MySqlPWParameter.ParameterName = "@用户密码";
                MySqlPWParameter.Value = this.用户密码TextBox.Text;
                MyCommand.Parameters.Add(MySqlPWParameter);
                int MyCount = (int)MyCommand.ExecuteScalar();
                if (MyCount == 1)
                {
                    this.Close();
                }
                else
                {
                          this.MyTryCount += 1;
                if (this.MyTryCount != 3)
                {
                    int MyDoCount = 3 - this.MyTryCount;
                    MessageBox.Show("用户密码或用户名称有错，还有" + MyDoCount + "次机会！", "信息提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    this.用户密码TextBox.Text = "";
                    this.用户名称TextBox.Text = "";                    
                }
                else
                {
                    退出系统Button_Click(null, null);
                }
                }
                if (MyConnection.State == ConnectionState.Open)
                {
                    MyConnection.Close();
                }
        }

Answer 4

            if (comboBox2.Text == "")
            {
                MessageBox.Show("用户名不能为空！");
                return;
            }
            if (textBox3.Text == textBox4.Text)
            {
                if (获取密码(comboBox2.Text) == textBox2.Text)
                {
                    OleDbConnection con = new OleDbConnection(通用数据.连接字符串);
                    string ss = @"UPDATE user1 SET password1 = '" + textBox4.Text + "' WHERE (num = " + 用户编号 + ")";
                    OleDbCommand com = new OleDbCommand(ss, con);
                    con.Open();
                    com.ExecuteNonQuery();
                    con.Close();
                    MessageBox.Show("修改成功！");
                }
                else
                {
                    MessageBox.Show("你输入的密码有误！请重试");
                }
            }
            else
            {
                MessageBox.Show("你两次输入的新密码不一致！请重试");
            }

Answer 5

            if (comboBox2.Text == "")
            {
                MessageBox.Show("用户名不能为空！");
                return;
            }
            if (textBox3.Text == textBox4.Text)
            {
                if (获取密码(comboBox2.Text) == textBox2.Text)
                {
                    OleDbConnection con = new OleDbConnection(通用数据.连接字符串);
                    string ss = @"UPDATE user1 SET password1 = '" + textBox4.Text + "' WHERE (num = " + 用户编号 + ")";
                    OleDbCommand com = new OleDbCommand(ss, con);
                    con.Open();
                    com.ExecuteNonQuery();
                    con.Close();
                    MessageBox.Show("修改成功！");
                }
                else
                {
                    MessageBox.Show("你输入的密码有误！请重试");
                }
            }
            else
            {
                MessageBox.Show("你两次输入的新密码不一致！请重试");
            }

Answer 6

        private string 获取密码(string usename)
        {
            string 密码 = "";
            try
            {
                OleDbConnection con = new OleDbConnection(通用数据.连接字符串);
                string ss = @"SELECT TOP 1 password1, num FROM user1 WHERE (name1 = '" + usename + "')";
                OleDbCommand com = new OleDbCommand(ss, con);
                OleDbDataAdapter da = new OleDbDataAdapter(com);
                DataSet ds = new DataSet();
                con.Open();
                ds.Clear();
                da.Fill(ds);
                con.Close();
                密码 = ds.Tables[0].Rows[0][0].ToString();
                用户编号 = ds.Tables[0].Rows[0][1].ToString();
            }
            catch { }
            return 密码;
        }