1 using System;
 2 using System.Collections.Generic;
 3 using System.ComponentModel;
 4 using System.Data;
 5 using System.Drawing;
 6 using System.Linq;
 7 using System.Text;
 8 using System.Threading.Tasks;
 9 using System.Windows.Forms;
10 using System.Text.RegularExpressions;
11 using System.Xml;
12 using System.Xml.Linq;
13 
14 namespace CheckInfo
15 {
16     public partial class Form1 : Form
17     {
18         public Form1()
19         {
20             InitializeComponent();
21         }
22 
23         private void textBox1_TextChanged(object sender, EventArgs e)
24         {
25             if (textBox1.Text == "请输入用户名，格式：qarootdc\\jqhuang")
26             {
27                 textBox1.Text = "";
28             }
29 
30         }
31 
32         private void textBox2_TextChanged_1(object sender, EventArgs e)
33         {
34             if (textBox2.Text == "请输入密码")
35             {
36                 textBox2.Text = "";
37             }
38         }
39 
40         private void button1_Click(object sender, EventArgs e)
41         {
42             if (isValidUserName(textBox1.Text) == false)
43             {
44                 MessageBox.Show("用户名格式不正确！请重新输入！");
45                 textBox1.Text = "";
46             }
47             else 
48             {
49                 //用户名格式正确.
50                 CheckUserAndPwd(textBox1.Text,textBox2.Text);
51             }
52         }
53 
54         private void CheckUserAndPwd(string username, string pwd)
55         {
56             //读取UserInfo.xml检测user是否存在
57             XDocument userInfo = XDocument.Load(@"C:\Users\jqhuang\Desktop\UserInfo.xml");
58             var result = from userElement in userInfo.Element("System").Element("users").Elements() where userElement.Element("username").Value.ToString() == textBox1.Text.ToString() select userElement.Element("pwd").Value;
59             if (result != null)
60             {
61                 foreach (var password in result)
62                 {
63                     if (password == pwd)
64                     {
65                         MessageBox.Show("用户名和密码匹配成功！");
66                     }
67                     else
68                     {
69                         MessageBox.Show("用户名和密码不匹配，请重新输入密码");
70                         textBox2.Text = "";
71                     }
72                 }
73             }
74             else 
75             {
76                 MessageBox.Show("您输入的用户不存在！");
77             }
78         }
79 
80         bool isValidUserName(string userName) 
81         {
82             return Regex.IsMatch(userName,@"^.+\\.+$");
83         }
84     }
85 }