密码由6-12位数字或字母组成，密码哈希加密

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            string pwdregex = "^[a-zA-Z0-9]{6,12}$";
            System.Text.RegularExpressions.Regex regPwd = new System.Text.RegularExpressions.Regex(pwdregex);
            if (!regPwd.IsMatch(PasswordBox1.Password.Trim()))
            {
                label_warning.Content = "提示：密码由6-12位数字或字母组成！";
            }
            else if (PasswordBox1.Password.Equals(PasswordBox2.Password))
            {
                MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
                byte[] str = md5.ComputeHash(System.Text.Encoding.UTF8.GetBytes(PasswordBox1.Password));
                string pwd = string.Empty;
                for (int i = 0; i < str.Length; i++)
                {
                    pwd += Convert.ToString(str[i], 16).PadLeft(2, '0');
                }
                try
                {
                    using (StockManageDataContext smDataContext = new StockManageDataContext())
                    {
                        string usrname = (this.Parent as LoginWindow).User;
                        var s = smDataContext.Users.Single(c => c.UserName == usrname);
                        s.Password = pwd;
                        smDataContext.SubmitChanges();
                        MessageBox.Show("密码添加成功！");
                        this.NavigationService.Navigate(new Uri("LoginPage.xaml", UriKind.Relative));
                    }
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                    label_warning.Content = "提示：密码修改失败！";
                }

            }
            else
            {
                label_warning.Content = "提示：两次输入的密码不同！";
            }
        }