wpf学习笔记之点登录按钮时判断用户名密码进行登录：动画系列之

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using User.sqlHelper;
using System.Data;

namespace User
{
    /// <summary>
    /// uc_login.xaml 的交互逻辑
    /// </summary>
    public partial class uc_login : UserControl
    {
        public uc_login()
        {
            InitializeComponent();
        }

        private void UserControl_Loaded(object sender, RoutedEventArgs e)
        {
            //获取下拉框用户名字
            User_test _u = new User_test();
            DataSet _ds = _u.GetList();
            if(_ds != null)
            {
                DataTable _dt = _ds.Tables[0];
                for (int i = 0; i < _dt.Rows.Count; i++)
                {
                    string UserName = _dt.Rows[i]["UserName"].ToString().Trim();
                    ComboBoxItem cbitem = new ComboBoxItem();
                    cb_uploader.Items.Add(cbitem);
                    cbitem.Content = UserName;
                }
            }
        }

        代码在这：                                    
        private static string loginname = "";
        //登录按钮
        private void btn_login_Click(object sender, RoutedEventArgs e)
        {
            //判断下拉框不为空
            if (this.cb_uploader.Text != "")
            {
                //判断密码不为空
                if (this.tb_password.Text != "")
                {
                    //从下拉框获取名字
                    string s1 = cb_uploader.Items[cb_uploader.SelectedIndex].ToString();
                    loginname = s1.Split(‘:‘)[1].Trim();
                    //从密码框获取密码
                    string password = tb_password.Text.Trim();
                    
                    //获取数据库的名字和密码
                    User_test _u = new User_test();
                    DataSet _ds = _u.GetList();
                    if(_ds != null)
                    {
                        DataTable _dt = _ds.Tables[0];
                        for (int i = 0; i < _dt.Rows.Count; i++)
                        {
                            //数据库取出name和psw
                            string UserName = _dt.Rows[i]["UserName"].ToString().Trim();
                            string UserPassword = _dt.Rows[i]["UserPassword"].ToString().Trim();

                            //先判断名字是否正确
                            if (loginname.Equals(UserName))
                            {
                                //再判断密码是否正确
                                if (password.Equals(UserPassword))
                                {
                                    this.Visibility = Visibility.Collapsed;
                                }
                                else
                                {
                                    MessageBox.Show("密码不正确！");
                                    tb_password.Text = "";
                                }
                            }
                        }
                    }

                }
                //密码为空
                else
                {
                    MessageBox.Show("请输入密码！");
                    return;
                }
            }
            //下拉框为空
            else
            {
                MessageBox.Show("请输入用户名！");
            }
        }
    }
}