通讯录管理系统，数据库关系模式为:账户(账户名,登录密码,头像)，联系人(ID,姓名,电话,QQ,Email)。主要功能包括：注册，登录，注销账号，修改账户名以及密码，更换头像，以及对联系人的增删改查。

工具：Visual Studio 2015,sql server2014

数据库关系表：

Account:                                                                           Contact:

 http://images2015.cnblogs.com/blog/865264/201605/865264-20160505225400419-2140861622.png                   http://images2015.cnblogs.com/blog/865264/201605/865264-20160505225848888-896174822.png

VS中主要界面及代码：

登录主界面：Login

http://images2015.cnblogs.com/blog/865264/201605/865264-20160505230235091-1205153169.png

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
 
namespace Contact_Manage
{
    /// <summary>
    /// 登录
    /// </summary>
    public partial class Login : Form
    {
        //存取用户登录名
        public static String txtLogin_Username;
        public Login()
        {
            InitializeComponent();
        }
 
        //登录
        private void btt_Login_Click(object sender, EventArgs e)
        {
            //获取用户输入的用户名和密码
            txtLogin_Username = tB_Account_Username.Text;
            String password = tB_Account_Password.Text;
 
            if (txtLogin_Username == "" || password == "")
            {
                MessageBox.Show("请输入用户名和密码！");
                return;
            }
 
            //连接数据库进行数据判断
            string sqlcon = "server=.;database=phone_Book;uid=sa;pwd=666888";
            String sqlcom = " select * from Account where Account_Username='" + txtLogin_Username + "' and Account_password='" + password + "'";
            SqlConnection con = new SqlConnection(sqlcon);
            SqlCommand com = new SqlCommand(sqlcom, con);
            con.Open();
 
            SqlDataReader reader = com.ExecuteReader();
            if (reader.Read())
            {
                //打开菜单页面
                Menu menu = new Menu();
                menu.Show();
            }
            else
            {
                MessageBox.Show("用户名或密码错误，请重新输入！");
            }
            con.Close();
 
            //清空文本框
            foreach (Control item in this.Controls)
            {
                if (item is TextBox)
                {
                    item.Text = "";
                }
            }
        }
 
        //注册账号事件
        private void lb_Regist_Click(object sender, EventArgs e)
        {
            Regist rigist = new Regist();
            rigist.Show();
        }
 
        //注销账户事件
        private void lb_Logout_Click(object sender, EventArgs e)
        {
            //跳出注销界面，验证输入的用户名及密码是否正确
            Logout logout = new Logout();
            logout.Show();
 
        }
 
        //点击密码文本框时将登录头像显示在pictureBox控件中
        private void tB_Account_Password_MouseClick(object sender, MouseEventArgs e)
        {
            //获取输入的用户名
            String username = tB_Account_Username.Text;
 
            if (username != "")
            {
                //连接数据库，如果该用户名存在则将头像显示
                string sqlcon = "server=.;database=phone_Book;uid=sa;pwd=666888";
                String sqlcom = " select * from Account where Account_Username='" + username + "'";
                SqlConnection con = new SqlConnection(sqlcon);
                SqlCommand com = new SqlCommand(sqlcom, con);
                con.Open();
 
                SqlDataReader reader = com.ExecuteReader();